User:Serendipodous/indigo/page 16

Aztec
Venus god of war, descent into the underworld, depicted as a heart

Sugimoto 2014
Ishtar

goddess of sexual love and behavior, connected with extramarital sex

a particularly warlike goddess. Battle is often described as the “playground of Ištar.” She stood beside her favorite kings as they fought.

She is identifi ed with the planet Venus, both the morning and the evening star. Some specialists believe that originally there were two Mesopotamian Venus deities: the Sumerian female Venus deity Inanna, identifi ed with the evening star, and the Semitic male Venus deity Athtar, identifi ed with the morning star.11 It is known that Inanna/Ištar has androgynous features. In a few cases, she is depicted as wearing a beard.12 She thus has a bi-sexual aspect.

Ištar always retains a major position with overwhelming power in the pantheon. She protects the king by her own will, and even if she intercedes for the king, she is standing before the chief gods of the pantheon or before the supreme divine council, that is to say, in a public place, whereas Tašmētu for example, intercedes with her husband in her bedroom,

She is identifi ed with the planet Venus, both the morning and the evening star. Some specialists believe that originally there were two Mesopotamian Venus deities: the Sumerian female Venus deity Inanna, identifi ed with the evening star, and the Semitic male Venus deity Athtar, identifi ed with the morning star

Sagan 1961
seltzer ocean, carboniferous swamp, or hydrocarbon surface

black body microwave emmission of 600 K

Either the ionosphere or actual temperature

and those planning eventual manned expeditions to Venus must be exceedingly perplexed over whether to send along a paleobotanist, a mineralogist, a petroleum geologist, or a deep-sea diver.

Petrov
hydrogen from acid?

sobel
Skidi Pawnee human sacrifice

260 days as morning star, 260 as evening star

cycsolsys
ESA 2016 Venus Express They found one particular area of cloud, near Venus' equator, to be hoarding more water vapour than its surroundings. This 'damp' region was located just above a 4500-metre-altitude mountain range named Aphrodite Terra. This phenomenon appears to be caused by water-rich air from the lower atmosphere being forced upwards above the Aphrodite Terra mountains, leading researchers to nickname this feature the 'fountain of Aphrodite'.

Scientists long have theorized that Venus formed out of ingredients similar to Earth's, but followed a different evolutionary path. Measurements by NASA's Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

D/H is a 150 times higher than Earth

water traps co2 as carbonate

water in earths interior weakens the strength of rock, which allows it to break into plates

dry basalt is stronger than wet basalt, so that the higher temperatures do not offset the lack of water

water may be required to form silica-rich continental crusts

ESA 2016 Venus Express They found one particular area of cloud, near Venus' equator, to be hoarding more water vapour than its surroundings. This 'damp' region was located just above a 4500-metre-altitude mountain range named Aphrodite Terra. This phenomenon appears to be caused by water-rich air from the lower atmosphere being forced upwards above the Aphrodite Terra mountains, leading researchers to nickname this feature the 'fountain of Aphrodite'.

Scientists long have theorized that Venus formed out of ingredients similar to Earth's, but followed a different evolutionary path. Measurements by NASA's Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

740K on the surface

Troposphere from 0 to 65 km; clouds from 50 to 65 km 65 to 95 km (mesosphere, stratosphere)

1932: Co2 detected

4 day rotation of the cloud tops 6ay rotation of the deeper region

People could not initially believe the recorded surface temperatures

Pioneer venus showed that the clouds were not water but h2so4

Venera 15 and 16 imaged about a quarter of Venus's surface using radar

Venera 4 id'd the gas as Co2 97% (96.5 vs 3.5% N2, with the rest measured in parts per million

Earth's atmosphere is mostly nitrogen, but Venus has about 3 times as much

D/H is a 150 times higher than Earth

tropopause at 65 km

water traps co2 as carbonate

Venus is the most volcanic planet in the Solar System (io is a moon)

In fact venus has no magnetic field at all

H2SO4 is colourless, so the yellow coloration must be caused by something else. Possibly sulfur? (models suggest too little- possibly ferric chloride)

lightning detectors on Cassini saw lighting on Earth but not on venus

we may have heard it, but no one has seen it

Mars has been largely inactive for the last 3 billion years

Venus, while it may not be active today, has been active in the last billion years

Fundamentally, a terrestrial planet is attempting to expel the heat generated by radioactive decay in its interior

0water in earths interior weakens the strength of rock, which allows it to break into plates

The venera landers measured baslatic composition

one venusian year lasts almost exactly 2 venusian days

sharp angular rocks suggesting minimal erosion

940 impact craters, ranging from 1.5 km to 270 km

few below 30 km in diameter, as atmosphere burns them up

impact craters are the only means of dating the surface suggesting an age of 750 Ma compared to 3-4000 Ma for the Moon and Mars

Impact craters appear to be randomly distributed

Only 17% show signs of tectonic or volcanic alteration

Few half-buried craters suggested initially global catastrophic resurfacing, though models have suggested that it may have occurred more piecemeally

dry basalt is stronger than wet basalt, so that the higher temperatures do not offset the lack of water

Several features on Venus resemble mantle plume bulges (10 compared to up to 30 for Earth

Coronae are likely the result of smaller plumes

Venus doesn't have a runny aesthenosphere to spread the punch- uplifts are far larger on Venus

lithosphere 100 to 200 km comprable to earth`

volcanism cannot be a major factor of heat loss now, since crater counts suggest little has taken place since the last resurfacing

heat loss is a likely method for a dynamo; hence, when venus lost plate tectonics, it lost its dynamo

most of venus's geological history has been erased

water may be required to form silica-rich continental crusts

Immediately after arriving at Venus in 2006, the spacecraft recorded a significant increase in the average density of sulphur dioxide in the upper atmosphere, followed by a sharp decrease. One possibility is that the dramatic swing in atmospheric composition was caused by buoyant plumes of volcanic gases released by a large eruption and floating upward. This is one of the major discoveries made by Venus Express.

impact crater count: older areas have m more craters- venus randomly distributed. Whole planet the same age?

erupting volcanoes? No fresh lava flows in 4 years of magellan

Magellan: highest mountain tops were bright and reflective, reflective radar energy- Tellurium?

Venus is mostly "oceanic" crust

Plains show evidence of flood basalts

shield and cone volcanoes

brightness/darkness in magellan is about ruggednes, not colour

crustal plateaus formed form compression after downwelling? Or from decompression after upwelling?

chasmata breaks from upwellings

2015 In combing through data from the European Space Agency's Venus Express mission, the scientists found transient spikes in temperature at several spots on the planet's surface. The hotspots, which were found to flash and fade over the course of just a few days, appear to be generated by active flows of lava on the surface.

The spots were clustered in a large rift zone called Ganiki Chasma. Rift zones are formed by stretching of the crust by internal forces and hot magma that rises toward the surface. Head and Russian colleague Mikhail Ivanov had previously mapped the region as part of a global geologic map of Venus generated from the Soviet Venera missions in the 1980s and U.S. Magellan mission in the 1990s. The mapping work had shown that Ganiki Chasma was quite young, geologically speaking, but just how young wasn't clear until now.

ESA 2016 Venus Express They found one particular area of cloud, near Venus' equator, to be hoarding more water vapour than its surroundings. This 'damp' region was located just above a 4500-metre-altitude mountain range named Aphrodite Terra. This phenomenon appears to be caused by water-rich air from the lower atmosphere being forced upwards above the Aphrodite Terra mountains, leading researchers to nickname this feature the 'fountain of Aphrodite'.

Scientists long have theorized that Venus formed out of ingredients similar to Earth's, but followed a different evolutionary path. Measurements by NASA's Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

Tesserae are tectonically deformed regions on the surface of Venus that are often more elevated than the surrounding landscape. They comprise about 7% of the planet's surface, and are always the oldest feature in their immediate surroundings, dating to about 750 million years old. In a new study appearing in Geology, the researchers show that a significant portion of the tesserae have striations consistent with layering.

"There are generally two explanations for tesserae—either they are made of volcanic rocks, or they are counterparts of Earth's continental crust," says Paul Byrne, associate professor of planetary science at North Carolina State University and lead author of the study. "But the layering we find on some of the tessera isn't consistent with the continental crust explanation."

"Continental crust is composed mainly of granite, an igneous rock formed when tectonic plates move and water is subducted from the surface," Byrne says. "But granite doesn't form layers. If there's continental crust on Venus, then it's below the layered rocks we see.

ESA's Venus Express has returned the clearest indication yet that Venus is still geologically active. Relatively young lava flows have been identified by the way they emit infrared radiation. The finding suggests the planet remains capable of volcanic eruptions.

BBC planets
Lamonosov 1761 transit of Venus- halo observed.

Everyone was expecting to find oceans on the surface

The soviets even included a trap made of sugar that would release the antenna when dissolved in water

The first transmission between Earth and another planet

At 15 atmospheres and 15 miles from the surface the probe stopped responding

They decided to proof their probes to 150 atmospheres

During one test, in a massive chamber designed to mimic the atmosphere of venus, they opened the door to find the probe wasn't there

it was oozing across the floor; only its lenses staring blankly upward like dead eyes

4 years later, Venera 7 reported touchdown

murky red light- overcast day

lightning hundreds of times more frequent than Earth; "the electric dragon of Venus"

too close to the surface, where there is no rain

1975 Venera 9: they didn't expect an image, so to keep expectations low they called their cameras telephotometers and contrast meters

systems intact on landing- image taken

Venera 11 and 12: cameras failed to open due to a design flaw

We have landed in something sticky and viscous "yes sir, in the shit"

Venera 14 and 14: arm measured the mechanical and electroconductive properties of its own lens cap

fool's gold? High reflectivity tops of mountains Iron compounds

pummeling the poor unprotected atmospheres of Venus and Mars, and tearing chunks of the planets off into space.

Christmas 2006, The stream of atmosphere escaping from the planet had become a river, and then a torrent. In all my time as a member of the scientific crew of Venus Express, I have never seen such an outflowing of the atmosphere. It was like someone stuck an invisible knife into the planet, and its skies were pouring blood out into space. glyn collinson slate

2014 Venus Express green emission deep atmosphere

close to the sun, flooded charged particles, no need for magnetic field

2015 Venus Xpress south polar vortex

lthough wind speeds are sluggish at the surface, they reach dizzying speeds of around 400 km/h at the altitude of the cloud tops, some 70 km above the surface. At this altitude, Venus' atmosphere spins round some 60 times faster than the planet itself. This is very rapid; even Earth's fastest winds move at most about 30% of our planet's rotation speed. Quick-moving Venusian winds can complete a full lap of the planet in just four Earth days.

Polar vortices form because heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks, it creates a vortex much like that found above the plughole of a bath.

"Other findings indicated that the planet continues to lose parts of its upper atmosphere to space, and that the 'super-rotating' atmosphere has seen wind speeds increasing from 300 km/h to 400 km/h over the last six Earth years."

Immediately after arriving at Venus in 2006, the spacecraft recorded a significant increase in the average density of sulphur dioxide in the upper atmosphere, followed by a sharp decrease. One possibility is that the dramatic swing in atmospheric composition was caused by buoyant plumes of volcanic gases released by a large eruption and floating upward. This is one of the major discoveries made by Venus Express.

The planet is completely socked in by cloud, which makes it extremely reflective to observers looking at the sky on Earth. Its brightness is between -3.8 and -4.8 magnitude, which makes it brighter than the stars in the sky. In fact, it's so bright that you can see it go through phases in a telescope—and it can cast shadows! So that remarkable appearance can confuse people not familiar with Venus in the sky, leading to reports of airplanes or UFOs.

The researchers have found yet another peculiarity of Venus' upper atmosphere: early in the morning it is warmer than in the evening, while it should be the other way round.

2015 In combing through data from the European Space Agency's Venus Express mission, the scientists found transient spikes in temperature at several spots on the planet's surface. The hotspots, which were found to flash and fade over the course of just a few days, appear to be generated by active flows of lava on the surface.

The spots were clustered in a large rift zone called Ganiki Chasma. Rift zones are formed by stretching of the crust by internal forces and hot magma that rises toward the surface. Head and Russian colleague Mikhail Ivanov had previously mapped the region as part of a global geologic map of Venus generated from the Soviet Venera missions in the 1980s and U.S. Magellan mission in the 1990s. The mapping work had shown that Ganiki Chasma was quite young, geologically speaking, but just how young wasn't clear until now.

Ashen light on Venus is either an illusion—a trick of the dazzling brilliance of a crescent Venus fooling the eye of the observer—or a real, and not as yet fully described phenomenon. Over the years, suggestions have included: lightning, airglow, volcanism, and aurora. A good prime candidate in the form of an 'auroral nightglow" was proposed by New Mexico State University researchers in 2014. 19th century astronomers even proposed we might be seeing the lights of Venusian cities, or perhaps forest fires!

Although winds on the planet's surface move very slowly, at a few kilometres per hour, the atmospheric density at this altitude is so great that they exert greater force than much faster winds would on Earth.

Winds at the 65 km-high cloud-tops, however, are a different story altogether. The higher-altitude winds whizz around at up to 400 km/h, some 60 times faster than the rotation of the planet itself. This causes some especially dynamic and fast-moving effects in the planet's upper atmosphere, one of the most prominent being its 'polar vortices'.

n the centre of the polar vortex, sinking air pushes the clouds lower down by several kilometres, to altitudes where the atmospheric temperature is higher. The central 'eye of the vortex' can therefore be clearly seen by mapping thermal-infrared light, which shows the cloud-top temperature:

"We found atmospheric gravity waves to be dominant in Venus' polar atmosphere," added Bruinsma. "Venus Express experienced them as a kind of turbulence, a bit like the vibrations you feel when an aeroplane flies through a rough patch. If we flew through Venus' atmosphere at those heights we wouldn't feel them because the atmosphere just isn't dense enough, but Venus Express' instruments were sensitive enough to detect them."

2016 Prof. Vladimir Krasnopolsky first questioned the "sulfur hypothesis" in 1986 by demonstrating that the amount was not enough to explain the effect of UV absorption. In the new paper, Krasnopolsky presents the first photochemical model of the formation of sulfur particles in Venus's clouds. In particular, the model includes certain processes of the breakdown of sulfur compounds under the influence of light that had not been factored into previous models. The resulting profile compiles the concentration of sulfur aerosol at various altitudes.

(FeCl3), which was discovered in the planet's atmosphere by the X-ray fluorescence spectrometer on board Venera 12.

ESA 2016 Venus Express They found one particular area of cloud, near Venus' equator, to be hoarding more water vapour than its surroundings. This 'damp' region was located just above a 4500-metre-altitude mountain range named Aphrodite Terra. This phenomenon appears to be caused by water-rich air from the lower atmosphere being forced upwards above the Aphrodite Terra mountains, leading researchers to nickname this feature the 'fountain of Aphrodite'.

Scientists long have theorized that Venus formed out of ingredients similar to Earth's, but followed a different evolutionary path. Measurements by NASA's Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

"In the GISS model's simulation, Venus' slow spin exposes its dayside to the sun for almost two months at a time," co-author and fellow GISS scientist Anthony Del Genio said. "This warms the surface and produces rain that creates a thick layer of clouds, which acts like an umbrella to shield the surface from much of the solar heating. The result is mean climate temperatures that are actually a few degrees cooler than Earth's today."

"Interestingly, every 11.07 years, the Sun and the planets Venus, the Earth and Jupiter are aligned. We asked ourselves: Is it a coincidence that the solar cycle corresponds with the cycle of the conjunction or the opposition of the three planets?" ponders Stefani. Although this question is by no means new, up to now scientists could not identify a plausible physical mechanism for how the very weak tidal effects of Venus, the Earth and Jupiter could influence the Sun's dynamo.

they postulate that the radiation observed emanating from Venus could be due to solar radiation interacting with Venus' magnetic field and being scattered along its tail. This would explain why from various studies, the radiation appeared to be coming from Venus' itself, thus extending and adding optical thickness to its atmosphere.

"We could identify and map distinctive lava flows from the top and eastern flank of the volcano, which might have been recently active in terms of geologic time," says Piero D'Incecco, planetary researcher at the DLR who is presenting these results today at the joint 48th meeting of the American Astronomical Society's Division for Planetary Sciences (DPS) and 11th European Planetary Science Congress in Pasadena, California.

Enter the Japanese spacecraft Akatsuki, which was launched on May 20, 2010. The spacecraft is designed to study the structure and activity of the Venus atmosphere. After a difficult journey, it was successfully inserted into orbit at the second attempt in 2015. This, along with the first few results, were a huge achievement.

The new study reporting the discovery of the bow-shaped structure, just published in Nature Geoscience, is the most recent result of the mission. The wave was caught by Akatsuki's imaging instruments – looking in the infrared and ultraviolet parts of the electromagnetic spectrum. The astronomers analysing the data noted that the structure extended 10,000 km through the Venus cloud tops and persisted for a few days, then suddenly disappeared.

Remarkably, the shape seems tied to the slowly rotating terrain below, particularly a high region called Aphrodite Terra, which is up to 5km high and the size of Africa near the equator. The structure persists in the rapidly moving, super-rotating winds at the cloud level. This is a bit like the flow of water flow around a submerged stone in a stream.

Earlier this year, the team demonstrated nearly identical silicon carbide integrated circuits for more than 1,000 hours at 900 degrees Fahrenheit in Earth-atmosphere oven testing. The integrated circuits were originally designed to operate in hot regions of fuel-efficient aircraft engines.

The model the team built was simple. They placed a quantity of finely ground sand in a bowl, added some water and then heated it from below. The team was not looking to recreate the entire Venus landscape, or even a portion of it. Instead, they were looking to explain the way that coronae (volcanic-tectonic looking features) are formed. Coronae are circular depressions with bulges in the middle surrounded by trenches.

In heating their bowl of mud, the researchers noted that a crust formed due to evaporation at the surface and then bulges formed as hot parts below the crust forced their way upward. Eventually, the material that was pushed from below (similar to Earth mantle plumes) pierced the surface and leaked out onto the surrounding surface (rather like a pie in the oven). As material leaked out, pressure was relieved, causing the bulge to deflate even as more material made its way through the puncture wound, which soon hardened, creating a small bulge in the center of a depression surrounded by trenches.

These dark structures revealed the massive presence of a still unknown compound that absorbs ultraviolet radiation and obscures the region where they get concentrated. Tracking them allowed to discover the "super-rotating" nature of Venus' atmosphere: while the planet takes 243 days to rotate around its axis, the atmosphere spins around the planet in only four days. "A wave with the size of the Y must play a key role in explaining why the atmosphere rotates sixty times faster than the surface, so it was crucial to understand it," says Peralta (IAA-CSIC).

is due to the fact that the wave pushes upward and concentrates the mysterious ultraviolet absorber.

This finding raises challenges for existing models of stationary waves. Such waves were expected to be formed by surface winds interacting with obstacles such as surface elevations–a mountain, for example. However, previous Russian missions involving landers have measured surface winds on Venus that may be too weak for this to be true.

"This establishes a stable stratification which prevents a long-lasting geodynamo and a planetary magnetic field. This is our hypothesis for Venus. In the case of Earth, we think the moon-forming impact was violent enough to mechanically mix the core of the Earth and allow a long-lasting geodynamo to generate today's planetary magnetic field."

Byrne could only conjecture, but he suspects one possibility is very slow convective movement in the mantle. With the thin crust at the surface sitting only tens of kilometers above the mantle, convective motion could slowly push or drag surface chunks along. But because an enormous spreading rift also exists around the equator of Venus, it's possible that a global spreading process systematically pushes these blocks, causing them to jostle and deform.

"Again, it's not plate tectonics," Byrne emphasized. "These are little chunks of land that just rotate and move around. But if we were to put seismometers on Venus, maybe you'd hear some of these chunks go off today."

The researchers report that the simulation did show a wave formed in the cloud tops, similar to that seen on the actual planet. But they also found that the braking effect caused by the atmosphere running into the mountains actually slowed the spin of the planet—the amount depended on the time of day. They found that on average, though, the effect was enough to cause up to two minutes of variation in planet spin speed—not enough to account for the observed seven minutes of variability, but enough to suggest other physical features could be playing a similar role.

Luckily, the idea behind NASA's new mission is not to land people on the inhospitable surface, but to use the dense atmosphere as a base for exploration. No actual date for a HAVOC type mission has been publicly announced yet. This mission is a long term plan and will rely on small test missions to be successful first. Such a mission is actually possible, right now, with current technology. The plan is to use airships which can stay aloft in the upper atmosphere for extended periods of time.

Prof Horinouchi said: "The asymmetry in super-rotation speeds in cloud tops in the northern and southern hemispheres might be caused by variability in the distribution of the so-called 'unknown' ultraviolet absorber, which plays a key role in regulating how much radiation from the Sun that Venus can absorb. Our results provide new questions about the atmosphere of Venus, as well as revealing the richness of variety of the Venus atmosphere over space and time."

2019 In all five scenarios, they found that Venus was able to maintain stable temperatures between a maximum of about 50 degrees Celsius and a minimum of about 20 degrees Celsius for around three billion years. A temperate climate might even have been maintained on Venus today had there not been a series of events that caused a release, or 'outgassing', of carbon dioxide stored in the rocks of the planet approximately 700-750 million years ago. "Our hypothesis is that Venus may have had a stable climate for billions of years. It is possible that the near-global resurfacing event is responsible for its transformation from an Earth-like climate to the hellish hot-house we see today," said Way. Three of the five scenarios studied by Way and Del Genio assumed the topography of Venus as we see it today and considered a deep ocean averaging 310 metres, a shallow layer of water averaging 10 metres and a small amount of water locked in the soil. For comparison, they also included a scenario with Earth's topography and a 310-metre ocean and, finally, a world completely covered by an ocean of 158 metres depth.

These highlands were thought to be formed of granitic rock, like Earth's continents, which required oceans of water to form.

Scientists at the Lunar and Planetary Institute (LPI), including undergraduate student intern Frank Wroblewski from Northland College, find that a volcanic flow on Venus' Ovda Regio highlands plateau is composed of basaltic lava, calling into question the idea that the planet might once have been Earth-like with an ancient ocean of liquid water.

Radar imaging from NASA's Magellan spacecraft in the early 1990s revealed Venus, our neighboring planet, to be a world of volcanoes and extensive lava flows. In the 2000s, the European Space Agency's (ESA's) Venus Express orbiter shed new light on volcanism on Venus by measuring the amount of infrared light emitted from part of Venus' surface (during its nighttime). These new data allowed scientists to identify fresh versus altered lava flows on the surface of Venus. However, until recently, the ages of lava eruptions and volcanoes on Venus were not well known because the alteratiion rate of fresh lava was not well constrained.

"Many scientists seemed surprised that this was even something worth investigating," Peplowski said. "The notion that there's a higher nitrogen concentration in the upper atmosphere than in the lower was outside people's range of thought."

Their findings uncovered the factors that maintain the super-rotation while suggesting a dual circulation system that effectively transports heat across the globe: the meridional circulation that slowly transports heat towards the poles and the super-rotation that rapidly transports heat towards the planet's nightside.

In the new study, the researchers used numerical models of thermo-mechanic activity beneath the surface of Venus to create high-resolution, 3-D simulations of coronae formation. Their simulations provide a more detailed view of the process than ever before.The results helped Montési and his colleagues identify features that are present only in recently active coronae. The team was then able to match those features to those observed on the surface of Venus, revealing that some of the variation in coronae across the planet represents different stages of geological development.

atmospheric disruption not yet seen elsewhere in the solar system has been rapidly moving at around 50 kilometers above the hidden surface, and has gone unnoticed for at least 35 years. This planet-wide cloud discontinuity can sometimes extend as far as 7500 kilometers, across the equator, from 30º north to 40º south, and happens at the lower cloud level, at altitudes between 47.5 and 56.5 kilometers. The researchers discovered that since at least 1983, this wall of acid clouds is periodically swiping the solid globe over five days at about 328 kilometers per hour.

The head of Russia's space agency said Friday that Roscosmos wants to return to Venus and bring back soil samples and build spacecraft that will surpass Elon Musk's rockets. Roscosmos chief Dmitry Rogozin said in an interview with state news agency RIA Novosti. "It was always a Russian planet". He said he wanted Russians—in cooperation with Americans or by themselves—to bring back the surface materials of Venus.

The solar tide in an ancient Venusian ocean is simulated using a dedicated numerical tidal model. Simulations with varying ocean depth and rotational periods ranging from −243 to 64 sidereal Earth days are used to calculate the tidal dissipation rates and associated tidal torque. The results show that the tidal dissipation could have varied by more than 5 orders of magnitude, from 0.001 to 780 GW, depending on rotational period and ocean depth. The associated tidal torque is about 2 orders of magnitude below the present day Venusian atmospheric torque, and could change the Venusian daylength by up to 72 days per million years depending on rotation rate. Consequently, an ocean tide on ancient Venus could have had significant effects on the rotational history of the planet. These calculations have implications for the rotational periods of similarly close-in exoplanetary worlds and the location of the inner edge of the liquid water habitable zone.

Tesserae are tectonically deformed regions on the surface of Venus that are often more elevated than the surrounding landscape. They comprise about 7% of the planet's surface, and are always the oldest feature in their immediate surroundings, dating to about 750 million years old. In a new study appearing in Geology, the researchers show that a significant portion of the tesserae have striations consistent with layering.

"There are generally two explanations for tesserae—either they are made of volcanic rocks, or they are counterparts of Earth's continental crust," says Paul Byrne, associate professor of planetary science at North Carolina State University and lead author of the study. "But the layering we find on some of the tessera isn't consistent with the continental crust explanation."

"Continental crust is composed mainly of granite, an igneous rock formed when tectonic plates move and water is subducted from the surface," Byrne says. "But granite doesn't form layers. If there's continental crust on Venus, then it's below the layered rocks we see.

Venus is a slowly rotating planet since it takes about two hundred and forty three terrestrial days to complete a round about itself. Its atmosphere is expected to rotate with the same rhythm as well, but in the case of Venus it takes only four days. The origin and motor of this superrotation is so far unknown, but the numerous waves present in the planet's atmosphere may play an important role. A study has just identified the nature of these waves for the first time.

The variations of brightness of the rings of the observed glory is different than that expected from clouds of only sulphuric acid mixed with water, suggesting that other chemistry may be at play.

Although the discovery team identified phosphine at Venus with two different telescopes, helping to confirm the initial detection, phosphine gas can result from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity. However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than those processes are capable of generating, allowing the team to rule out numerous inorganic possibilities. But our understanding of the chemistry of Venus' atmosphere is sorely lacking:

First and foremost, we need more information about the abundance of PH₃ in the Venus atmosphere, and we can learn something about this from Earth. Just as the discovery team did, existing telescopes capable of detecting phosphine around Venus can be used for follow-up observations, to both definitively confirm the initial finding and figure out if the amount of PH₃ in the atmosphere changes with time. In parallel, there is now a huge opportunity to carry out lab work to better understand the types of chemical reactions that might be possible on Venus—for which we have very limited information at present.

The giant explosions, called hot flow anomalies, can be so large at Venus that they're bigger than the entire planet and they can happen multiple times a day.

(Phys.org) —The planet Venus is blanketed by high-level clouds. At visible wavelengths, individual cloud features are difficult to see, but observations made by instruments on ESA's Venus Express orbiter have revealed many small-scale wave trains. Analysis shows that the waves are mostly found at high northern latitudes, particularly above Ishtar Terra, a continent-sized region that includes the highest mountains on the planet.

Venus Express has revealed a planet of extraordinarily changeable and extremely large-scale weather. Bright hazes appear in a matter of days, reaching from the south pole to the low southern latitudes and disappearing just as quickly. Such ‘global weather’, unlike anything on Earth, has given scientists a new mystery to solve.

Greek mathematician Pythagoras sweated out the orbits of Venus, eventually becoming the first to determine that what had been believed to be unique and separate evening and morning stars (as believed by the ancient Egyptians and Greeks), was actually just one object - Venus.

The astronomers were stunned when they checked landmarks against the last mapping of Venus, carried out between 1990 and 1994 by the US probe Magellan.

At a given point in the Venusian day, landmarks were a full 20 kilometers (12 miles) behind where they should have been.

The team, publishing in the journal Icarus, say they have been over the observations again and again.

"After eliminating possible sources of error, we believe that the duration of the Venusian day must have changed over the 16 years," they said in a press release.

Their calculation is that an extra six and a half terrestial minutes have been added to the Venusian day during this time. Pendulum effect.

We have analyzed 3.5 Earth-years of Venus lightning data using the low-altitude Venus Express data (10 minutes per day). By comparing the electromagnetic waves produced at the two planets, we found stronger magnetic signals on Venus, but when converted to energy flux we found very similar lightening strength,”

The image taken on 26 February 2007 shows the 'classic' dipole shape at the centre of the vortex, similar to that which has been observed previously. But an image taken a mere 24 hours earlier shows the centre of the vortex to be almost circular, indicating that the shape of this feature can change very fast. At other times, it is typically oval.

In analyzing data obtained from Venus Express, the probe sent by the European Space Agency, the researchers found that on Venus, the solar wind reacts with the ions in its ionosphere and in one instance resulted in what they describe as a magnetic plasma bubble stretching for some 2100 miles and lasting for just over a minute and a half. This they say is also an example of magnetic reconnection, albeit, one of a different kind.

For years, researches have puzzled over mysterious flashes of light coming from Venus, and some have even speculated that they might be caused by magnetic reconnection, but until now lacked evidence. This new research adds strong credence to that theory and may also explain how some comet tails manage to disengage from their heads.

Venus Express has measured the rate of this escape and confirmed that roughly twice as much hydrogen is escaping as oxygen. It is therefore believed that water is the source of these escaping ions. It has also shown that a heavy form of hydrogen, called deuterium, is progressively enriched in the upper echelons of Venus’s atmosphere, because the heavier hydrogen will find it less easy to escape the planet’s grip.

Jean-Loup Bertaux, Service d’Aeronomie du CNRS, Verrières-le-Buisson, is the Principal Investigator for SPICAV. “I am very sceptical about the volcanic hypothesis,” he says. “However, I must admit that we don’t understand yet why there is so much SO2 at high altitudes, where it should be destroyed rapidly by solar light, and why it is varying so wildly.”

Venus Express has shown that the amount of hydroxyl at Venus is highly variable. It can change by 50% from one orbit to the next and this may be caused by differing amounts of ozone in the atmosphere.

James expected to find remnants of these crustal structures on Venus, given that they are prominent features on Mars and the moon. He believes that the absence of mascons is consistent with the idea that the Venus surface experienced some sort of “catastrophic overturning” at least 500 million years ago. “If the mascons were erased in the event 500 million years ago, that would require a mechanism that more thoroughly reworks the crust,” he explained.

2008 Although radar systems have been used in the past to provide high-resolution maps of Venus's surface, Venus Express is the first orbiting spacecraft to produce a map that hints at the chemical composition of the rocks. The new data is consistent with suspicions that the highland plateaus of Venus are ancient continents, once surrounded by ocean and produced by past volcanic activity.

Perhaps the most dramatic discovery was a steady increase in the mean cloud top wind speeds at low latitude from around 300 km/h to almost 400 km/h (80 - 110 m/s) in the period 2006 - 2013.

ome of the reasons being advanced for the spot in Venus' atmosphere include:


 * Volcanic eruption. (This option is considered unlikely, since the thick atmosphere would likely block most volcanic activity from being visible to us.)


 * Charged particles from solar interaction with Venus' atmosphere.


 * Atmospheric turbulence concentrating bright material in a confined area.

Ozone has only previously been detected in the atmospheres of Earth and Mars. On Earth, it is of fundamental importance to life because it absorbs much of the Sun's harmful ultraviolet rays. Not only that, it is thought to have been generated by life itself in the first place.

ESA's Venus Express has returned the clearest indication yet that Venus is still geologically active. Relatively young lava flows have been identified by the way they emit infrared radiation. The finding suggests the planet remains capable of volcanic eruptions.

Kuiper belt
Instability, in fact, is not due to close encounters with the planet, but to the overlapping of its outer mean-motion resonances.

Mean-motion resonances become wider at larger eccentricity and resonance overlapping produces large-scale chaos

The work since 1992 has been conducted largely by individuals or small groups (TGT)

It has unified a number of populations that were once studied in isolation. KBOS, centaurs, jFCs, even the moons of giant planets

Debris discs with non-primordial dust, continuosuly replenished presumably by internal collisions, could be extrasolar kuiper belts

Resonant KBOs (like Plutinos) likely trapped as Neptune migrated outward

the HTC/NIC population with 20 < P < 200 yr and TJ < 2 shows a very nearly isotropic distribution of inclinations with a median inclination near 80◦ . the high number of kbo binaries suggests that the belt was 100 to 1000 times more massive in the past than now

Collisional grinding would not have left so many large objects so the likely candidate is ejection

Nice model or 5 oligarch model

did the LHB happen at all>

KBOs are observed over very short arcs, Pluto has completed just 46 percent of its orbit since its discovery

there is a steep power law in the sizes of Kbos, Uncertzainty as to how the law evens out at the lower end has meant that estimates of the Kuiper belts mass have ranged from 0.01 to ~0.3 Em

the kbs mass deficit is similar to the asteroid belt

redder tnos/centaurs have a higher albedo than greyer ones

spitzer can detect low level infrared radiation from tnos and centaurs

thermal observations of tnos with stallites has allowed their density to be determined

no other objects than the haumea family exhibit both a grey color and deep water absorption lines (?)

cryovolcanism (?)

high albedo ice (frozen atmpsphere?)

Largest objects are likely spheroidal, variations in light curve due to brightness variation

measuring both visible light and infrared from an object can give an idea of its albedo

cold classical objects are very red, while high inclination objects run the gamut from red to grey

measured densities of TNOs run from 0.5 to 3

the red spectra are matched by tholins

TNO surfaces are modified by cosmic rays and uv radiation

the cold and hot populations have both different colors and different size distributions

Only a fraction of KBOs have their orbits determined; many are lost after just one observation

A TNO may have a very short lifetime in one particular orbit, yet must be classified according to its current orbit

Centaurs are defined as objects with a T parameter of 3.05 (outside of Jupiter's influence, a semi-major axis of at least 7,.35 AU and an aphelia below that of Neptune

Where a = 2000 AU+ there is a shift in dynamics, inicating a new population

To be in a resonance, an orbit must librate around a current value

SDOs qualify if their (marsden et al) aphelions migrate 1.5 AU or more over 10 million years

Ices display their most prominent absorption lines at frequencies below 1 micrometre, so standard spectrographs, which focus on visible light, were useless to detect them

the first water detected beyond earth (near infrared spectroscopy) was by gerard Kuiper in 1957, inthe moons of Jupiter and the rings of Saturn

Pluto atmosphere June 9 1988 KAO (45000 feet)

robert Mills Larry wasserman Lowell observatory

May 1992: methane detected in atmosphere, CO and N ice found on surface, must be part of atmosphere, far more volatile than methane

atmoshpere 99 percent N

1985 first detection of a transit around pluto's disc

a few years ever 124 years

Leif Andersson, swedish planetary scientist

hired by gerard kuiper shortly before his death

died at just 35 from lymphatic cancer

ice on charon and many other outer solar system bodies is in hexagonal phase, when at its temperature it should be in amorphous phase,.

Charon also fetures ammonia on its surface, which should be destroyed by UV light from the Sun. Is Charon geologically active?

oparin, primordial soup

carbonaceous meteorites have been found with up to 80 different types of amino acid, including most of the 29 used by life. Formed in liquid water in their parent asteroids

Carl sagan studied under miller and Urey, coined the term "tholin" from the greek word for muddy, after creating it in the lab

simulating titan's atmosphere, created tholin

renu Mahotra first proposed that Pluto and Charon migrated into their current 3:2 resonance with Neptune

renu mahotra first formulated the nice model

models have shown that evolution within the resonance would have produced Pluto's currently eccentric orbit- inclinaton is harder, and may be due to multi planet perturbations

Pluto likely gained Charon when it was in its low-eccentricity, low inclination orbit

TNOS are defined by where they are today, not where they will be in future or were in the past

The flood of KBO discoveries post QB1 made followup observations to determine orbits nearly impossible

brightness, pointing bias, but also poorly defined ephemeris

also slow movement

cold classical (35%) lo e lw i. 42.5 to 44.5 AU

hot classical (65%) hi e and i within 15 degrees. 35 and 47 AU. May be an extension of the detached population

Some TNOs are far redder than objects in the inner solar system, but neutral objects have also been found

the cold classicals are redder than other populations

Centaurs: peri> Jupiter, semi< Neptune (IAU) (Hidalgo?)

more objects are perturbed outward from the KB than inward

Centaurs have lifetmes of 1 million years or so

about 6 percent of centaurs become neos

models suggst that JFCs can evolve back into centaurs, though this is untestable via observation

there are believed to be about 10 million centaurs with a diameter larger than 2 km and about 100 centaurs with a diameter larger than 100 km

The mass of the centaurs is believed to be about 10 times larger than the mass of the asteroid belt

red centaurs have ancient surfaces, grey centaurs have had their surfaces destroyed, sublimating subsurface material

or it coudl be primordial. A distance of <40 AU alows bright methane ice to condense on the surface

albedo difference, elongation due to high angular momentum, or contact binaries. given their fast rotation periods (av. 8.5 hr, faster than the asteroids) they must be very porous, with densities less than water

The alrgerst kbos have high albedos, (60%) while smaller kbos have dim albedos (25%)

Hot classicals are blue/grey, cold classicals are red and contain pristine compounds, liek methanol

Once objects in a forming system reach r=1000 km, they begin to stir up the materials around them, increasing their velocities and collisional speeds, grinding them down before they can accrete

Nice model

flybys by other stars

there are no large objects in the cold classical belt

no formation model can explain this unless the cold and the hot belt formed in different places

closer to the sun, growth times were faster and densities were higher

comets formed in the region of the giant planets, and were initially scattered by them

debris discs remain opaque for 1-10 million years

during this transition, the planets form

observations of young stars suggest this formation period lasts about 100 thousand years

dust production post formation requires an initial mass of 10-100 earth masses

dust grains to aggregates, aggregates to planetesimals, planetesimals to planets, all increasingly independent of the gas

As objects collide, they lose energy, slowing down

As they grow larger, they disturb the orbits of smaller particles, in turn slowing them down

as oligarchs reach their maximum sizes, their gravity begins to cause objects to collide more forcefully, causing them to break apart instead of accreeting. This leads to a Kessler effect

Victor safranov

max r for cold 400 km

max r for hot 1000

resonants are broadly in line with the hot

Oorts original model could not explain why there were so few returning OC comets compared to new ones, cometary fading has been suggested as a solution

Hills argued that the 10-20000 AU inner edge of the OC may be a selection effect, because farther in comets were too rarely disturbed by close stellar passages

OC comets are initially scattered by the planets

100 thousand years a star with a fusing mass passes within 1 pc of the sun

galactic tide is arguably a greater contributor to OC comets than star passages

the jupiter barrier lowers the observed number of oc comets

Eris has a spectrum indicating a surface of near pure methane, as opposed to Pluto, which suggests methane mixed with nitrogen

lack of rotational features suggests that its atmosphere has frozen over its bedrock

spitzer and 100% albedo estimates suggest a diameter of sedna 1200 to 1600 km

sedna is one of the reddest objects in the solar system (tholins with nitrogen and methane frost)

Sedna is too far out for much of an atmosphere to form

Makemake is unusual in being largely dominated by methane ice, rather than nitrogen

haumea has a deep water ice absoroption lines, as do its family, which also share its dynamical position

Haumea's 12:7 resonance with Neptune has caused its orbital velocity at 500 m/s from its siblings

binaries in the KB tend to be of equal size, a discovery at variance with observations in the main belt and not entirely due to observational bias (HST)

this indicates that most binaries formed by capture

the vast majority of binaries are closely separated, which is strange because observational bias would favour widely separated objects.

larger tnos have densities of 2 or higher, suggeesting rocky material; smaller kbos have densities of less than 1

tidal flexing tends to produce mutual co-rotation

TNBs are unlikelty to have formed by fission, though whether they can split as comets do has not yet been explored.

"L2" hypothesis, with captured body slowed by "sea" of smaller bodies, more likely than 3 body capture. given high angular momentum this is teh most likely form of binary formation

pluto charon formed by collision?

Pluto and Triton are the only known objects in the region known to have atmospheres

albedos of 60 to 90- percent for distant kbos suggest a frozen atmosphere

cold classicals have long period binaries that would not have survived scattering

the break in size law at 30 km suggests that a collisional evolution followed a period of oligarchic growth and also suggested that the KB is the same as other interstellar debris discs SDOs are estimated to comprise a population of 60 thousand objects above 100 km

All have a peruihelion close to Neptune's orbit

semimajor axis 50 AU to 500 AU

the concentration of observed smaller semimajor axes may be a selection effect

those with perihelia above 38 AU are considered detached

SDOs are so weakly hound to the Sun that their semimajor axes can fluctuate either regularly through interaction with the planets, or through disruption

they can be caught in temporary mean motion resoannces

Pluto may expel the less stable objects into the JFC population

kbos are mainly rubble piles, which should enhance their ability to produce shrapnel

instabilities in the kb can expel objects into the scattered disc

0.14 Em for the TN region 0.08 Em for the SD

models suggest it is far easier to create a 44.4 AU perihelion but with a smaller a than CR105, so we should have found a great many other small a 105s

assuming sd is source of all cs and there are a total of 10 million cs than sd sends one centaur per year into the inner solar system

trojans
About a thousand trojans each have been observed at J l4 l5, though there are expected to be tens of thousands in total.

Neptune trojans are slightly red, like j trojans and neutral, less red centaurs.

Sheppard and trujillo have argued that the N Trojans and J trojgans share a common origin with the irregular satellites and the hot classicals

classical model: Jupiter got big fast, and captured objects near its orbit

Problem: inclinations should be similar to the primordial disc, but trojan inclinations range as high as 40 degrees

Some speculated that their orbits could have been disturbed by giant planetary embryos in the past, but there would have to have been an equal number of them in each wing

Nice model

Trojans have more elongated rotation curves and so are likely more elongated than the main belt objects

more like post active or active comets than pre active (centaurs)

densities of trojans measured from satellite orbits suggest that they range from comprable to MB asteroids, comet nuclei and TNOs

the spectra of most trojans are similar to those of d type asteroids

water ice has not been detected in their spectra

high eccentricity in the initial formation would have stripped them of their volatiles

c type asteorids, coet nuclei and less red centaurs

there don't appear to be any carbon compunds that generate quite the same type of red seen in the trojans (fine grained silicates?)

if the trojans formed in situ, then tehy should be similar to asteroids; if tehy formed in teh outer disc, then tehy should be similar to comets

the trojans are homogenous with featureless spectra

redder objects have higher inclinations (?)

centaurs appear to have more in common with comets than centaurs or TNOs, suggesting that they may have had orbits that took them close to the Sun before being captured

ecliptic comets
Ecliptic comets comprise halley type comets, encke type comets and centaurs

JFCs have chaotic orbits due to their interaction with jupiter

Encke type comets are old JFCs whose orbits have migrated within that of Jupiter

collisions likely play a role in placing objects in resonances

jfcs are likely broken fragments from collisions

scattered disc is likely source of JFCs

long period comets likely originated in the planetary region, from whence they were expelled to form the Oort cloud

approximately 1/3 of LPCs are first timers

oort cloud comprises 1 trillion comets

ebb flow tide

jfcs are strikingly carbon poor compared with Htcs and Lpcs

studies of comets suggest a far shallower size distribution for small kbos

satellites
outer irregulars have orbital periods of 1-10 yr

Jupiter's irregulars have low albedos (4-5%) similar to C, P and D asteroids and the Jupiter Trojans

Irregulars are grouped into families, sharing axis, inclination and eccentricity. Likely former satellites disrupted by collisions

families can be prograde or retrograde. Jupiter has three, maybe 4

phoebe inlcination group 170 degrees

saturn's irregulars are redder than jupiters but not as red as KBOs

iapetus dust is likely from these satellites

though not phoebe which is neutral colored, unlike nearly every other irregular, mulilfari excepted

e3xcept maybe yes since particles from the phoebe ring could infall onto Iapetus

groups cluster by color and inclination, rather than axis

Phoebe is by far the largest of Saturn's iregular satellites

himalia absorbtion iron oxide in phyllosilicates, formed in aqueous solution

dynamic division of the kbos, excited less red

neutral to red spectra Jupiter erregulars albedo color similar to outer c type asteroids

Phoebe and Nereid volatiles and strong water ice

high inclination jovian satellites are vulnerable to instability, leading to likely crashes into the galieans

four body capture (sun planet satellite satellite) is possible either with the capture of a binary or the interaction between two migrating giant planets

rivers flow

orbits pulse and throb as they are yanked by the sun and other planets

a group or a statistical cluster (pasiphae)

some groups look like collisional families, but some are too widely spaced for that to be likely

himalias anakes and carmes all share colors among themselves

there are virtually no km sized impactors in the region today

phoebe's density is higher than the inner satellites of saturn

nereid prograde icy spectrum. Originally regular?

cyc solar system
satellites jupiter and beyond mostly water ice ch4 nh3 ci2 sci so2

Phoebe Uranian satellites covered in C-type material

Primordial material orbits are like blood spatter at a crime scene, it can reveal more about the history than the objects themselves

Interactions with planets can lead to collisions, or having orbits shifted.

The moment you introduce a second planet, you introduce chaos; cometary orbits are chaotic by nature

A starting difference of one centimetre can produce a completely different orbit

Comets are also active, and thier orbits are affected by the action of sunlight and the solar wind

Planets orbits are predictable across 100s of millions (but not billions) of years, but comets orbits are unpredictable sometimes on the order of 100 years

Comets orbits cannot be realistically redicted or retrodicted. Only modelled.

Kozai mechanism, when the eccentricity and inclination of an orbit fall into resonance, leading to massive changes in one or the other, though not in semi-major axis, which means large changes in perihelion. The gravity of the galaxy has the same effect

effects of other objects in the solar syste, and the wider galaxy

300m year occilations

Decadal survey
the TNOs may tell us more about the giant planets than the giant planets themselves

any object that has come within Neptune's Hill's sphere within the age of the solar system is called a scattered disc object (proposal, 2003)

too evolved to offer clues as to the formation of the solar system

most kbos have eccentric or inclined orbits, suggesting past excitation

the original accretion disc must have had low inclination and eccentricity

resonances (3:4, 2:3, 1:2 and 2:5) and classicals

earlier belt was more massive and dynamically colder, allowing accretion rather than destruction

massive primordial kb (10 ME) required to eexplain alrge objects and binaries

classical belt has inclinations ofup to 32 deg and eccentricities up to 0.2, not a primordial disc

high and low inclination classicals

do the two populations share an origin or are they completely distinct

hots are bright and grey, colds are dark and red

the division lies the boundary between the hot and cold; they are different populations

Fernandez and Ip 1984 proposed that scattering planetesimals would have migrated Neptune outwards

mean motion resonances also migrated outwards, sweeping the belt clean until they reached their present position

as resonances swept the kuiper belt, they would have trapped various objects within their resonances, which migrated outward with them and increased their eccentricity.

this capture was from the scattered disc, not the classial belt

neptune's migration wouldhave to have been smooth; large, lunar sized objects would have stalled the migration of the resonances

some of these migrating resonant objects were snagged by a quirk of their orbit and trapped in the classical belt

Kuiper cliff, a mars sizedbody with 4% albhedo at 50-0 AU would have been found

accretion takes longer the farther out you go and planetesimals eventually drift inward due to gas drag

stellar encounter

Reservoirs: Oort cloud Kuiper belt trojans and satellites outer asteroids interstellar

Levison 2006
Like dust for fingerprints, or blood spatter, the orbits of the comets can reveal the history of the Solar System

Protoplanetary disc- first river?

comets orbits chaotic. can collide with planets, but more lilely the gravity of the planet will slingshot a comet from one orbit to another

planets have precessions triggered by their gravitational interactions between 47 thousand and 2 million years for the outer solar system

chaos is about prediction. Varying the orbit of Chiron by 1 cm produces vastly different orbital evolutions

Chaos means we cannot deterine which comet came from which reservoir. All that can be done is model the solar system and see where each comet ends up

Non gravitational forces increase the orbit of Halley by 4 days every orbit

Kozai, when ώ and Ω come into resonance. This allows eccentricity and inclination to make huge changes at the expense of the other. Can also change perihelion, though not semi-major axis

Kozai will drive makholtz into the sun in 12000 years, and also drove SL9 into Jupiter

galactic tide will eccentricity and inclination, but not semi major axis

passing stars can pull semi major axis outward

the 200 year distinction between SPs and LPs is purely historical. Since comets have only been predictable for 200 years, an orbit of less than 200 years allows an apparition to be checked in records.

Tessarand parameter, an quation derived from Jupiter's orbit. Those with a T of greater than 2 are called Nearly isotropic comets

Those with T smaller than 2 are called ecliptic comets.

peak at 20,00 AU- first appearance

Those with a <20,000 AU are likley those that have already gone through the rinse a few times

To be seen on Earth, a NIC needs to encounter a planet; these are somewhat optimistically called "returning" comets, even though they techincally aren't any more returning than "new" comets.

Halley type comets are those returning comets with orbits small enough to be caught in mean motion resonances with the outer planets.

Swift tuttle 11:1

Ecliptic comets

2>T>3 Jupiter family T>3 cannot cross the orbit of Jupiter, but interior to Jupiter, encke type >3 exterior to Jupiter, Chiron type

Chiron currently controlled by Saturn, both a comet and a centaur

two groups two reservoirs, oort cloud scattered disc

dynamical lifetime of a JFC is just 300000 years

Oort cloud Last structure in the solar system, ends at tidal truncation radius 100-200000 AU

inner edge betwween 2 and 5 thousand AU (uncertain)

Because new oc comets have sma of 20000 AU, Oort believed it must be the clouds inner edge

But oc comets must originate in a region in which the gt is strong enough to knock them past the giant planets in one push, otherwise theyd just be sent back again (20000 AU!)

Because many HT comets though ironically not halley itself have prograde orbits, it is surmised that the oort cloud must have a flattened inner region

27 percent of comets lie at ~4AU

Kuiper belt scattered disk?

sdos can gradually be slowly pulled outward until the galactic tide takes them to the oort cloud, or they can be sent inward by Neptune

The scattered disc contains about 1 percent the material it had 4 billion years ago

About a third of Neptune crossing comets becomes a Jupiter family comet

KBOS (classicals and resonant) are stable throughout the age of the solar system

For accretion to occur, objects relative orbit speeds must be small. But comets today have vastly different inclinations and eccentricities, giving them vastly different relative speeds. Therefore they could not have formed on their current orbits.

Comets formed in the region now occupied by the giant planets.

Jupiter sends a comet outward, which is then caught and supercharged by Neptune, over many many orbits, until its orbit becomes long enough to be affected by galactic tide.

The current kb could only create an object of 30 km, over the age of the solar system

Is the SD sustained by a rain from the KB, like the NEAs are sustained by a rain from the AB?

Or is it simply the remains of a much larger population, gradually depleting?

The latter is most likely true, since the SD is about as populated as the KB, wheras if the former was true the SD would be far less populated than the KB

Astronomers initially expected all KBOS/centaurs to be red

Instead, two distinct populations, one red, one grey, emerged. This distinction is real, and not due to sampling error

If it were due to grey cratering of red surfaces, it would be far less homogenous than it appears (random)

Instead it appears to be the remenants of a former composition/temperature gradient

OSSOS 2019
The dynamical evolution of the early Solar System was reviewed in Nesvorn´y (2018). Here we consider a class of models with slow, long-range and grainy migration of Neptune, because these models were the most successful in reproducing the orbital distribution of KBOs (e.g., Nesvorn´y & Vokrouhlick´y 2016; see Hahn & Malhotra 2005, Levison et al. 2008, Nesvorn´y 2015 for related models). In brief, the outer planets are assumed to start in a resonant chain with Neptune initially at ≃22-24 au. A massive outer planetesimal disk is placed from outside of Neptune’s initial orbit to ∼30 au. The disk is dispersed during Neptune’s migration with small fractions of the initial population of planetesimals ending on dynamically hot orbits in the present-day Kuiper belt.

The original outer disk is thought to have mass 15-20 M⊕ (Nesvorn´y & Morbidelli 2012), where M⊕ is the Earth mass, and a size distribution similar to that of today’s observed Jupiter Trojans (Morbidelli et al. 2009). The suggested relation to Jupiter Trojans hinges on a capture model from Nesvorn´y et al. (2013) (also see Morbidelli et al. 2005). Specifically, the Jupiter Trojan capture probability found in Nesvorn´y et al. (2013) is 5 × 10−7 for each outer disk planetesimal. There are 25 Jupiter Trojans with diameters D > 100 km, which implies that the outer planetesimal disk contained 5×107 D > 100-km planetesimals. Below 100 km, Jupiter Trojans have cumulative size distribution N(>D) ∝ Dγ with γ = −2.1 (Emery et al. 2015). From this we infer that the outer planetesimal disk contained 6 × 109 D > 10-km planetesimals (Nesvorn´y 2018).

According to these models, Neptune’s migration can be divided into two stages separated by a brief episode of dynamical instability (jumping Neptune model). Before the instability (Stage 1), Neptune migrates on a circular orbit. Neptune’s eccentricity becomes excited during the instability and is subsequently damped by a gravitational interaction with disk planetesimals (Stage 2). Here we produced two different models corresponding to two different migration histories,

We identified all objects that evolved onto Centaur orbits in our simulations and tracked their orbits back in time to establish their orbital histories. All these objects started in the original planetesimal disk below 30 au (Section 2). Figure 3 shows their orbits 1 Gyr ago when they resided in the trans-Neptunian region beyond 30 au. We find that 89% of Centaurs had Kuiper belt/scattered disk orbits with a < 5000 au and 11% were in the Oort cloud (a > 5000 au). For comparison, Nesvorn´y et al. (2017) found that 95% of ecliptic comets (orbital period P < 20 yr and the Tisserand parameter with respect to Jupiter 2 < TJ < 3). evolved from orbits with a < 200 au and 95% of Halley-type comets (20 < P < 200 yr, TJ < 2) evolved from the Oort cloud.

The source orbits of Centaurs show strong preference for a < 200 au (85% of the total). Of these, 31% have a < 50 au and 54% have 50 < a < 200 au. In this sense, the scattered disk beyond 50 au is the main source of Centaurs, but the contribution from the classical/resonant Kuiper belt at 30 < a < 50 au is also significant. For comparison, 20% of ecliptic comets come from 30 < a < 50 au and 75% from 50 < a < 200 au (Nesvorn´y et al. 2017). The preference for the scattered disk is therefore more pronounced for the ecliptic comets than for Centaurs. Also, 68% (76%) of Centaurs evolved from orbits with q < 35 au (q < 36 au) and a < 200 au, which shows that the source orbits are typically at least marginally coupled to Neptune. This makes sense because the trans-Neptunian orbits with q > 36 au are generally more stable and less often evolve to become planet crossing.

Fernandez 2018
We find that the median lifetime of inactive Centaurs is about twice longer than that for active Centaurs, suggesting that activity is related to the residence time in the region. This view is strengthened by the observation that high-inclination and retrograde Centaurs (Tisserand parameters with respect to Jupiter ) which have the longest median dynamical lifetime ( yr) are all inactive. We also find that the perihelion distances of some active, comet-like Centaurs have experienced drastic drops of a few au in the recent past ( yr), while such drops are not found among inactive Centaurs.

Inactive Centaurs with usually evolve to Halley-type comets, whereas inactive Centaurs with  and active Centaurs (that also have ) evolve almost always to Jupiter family comets and very seldom to Halley type comets.

Fouchard 2014
the largest stellar perturbations that may statistically be expected during the age of the Solar System induce a large scale migration of comets within the cloud. Thus, comets leave the inner parts, but the losses from the outer parts are even larger, so at the end of our simulations the Oort cloud is more centrally condensed than at the beginning. The decoupled comets, which form a source of centaurs and Halley type comets (roughly in the proportions of 70% and 30%, respectively), are mainly produced by planetary perturbations, Jupiter and Saturn being the most efficient. This effect is dependent on synergies with the Galactic tide and stellar encounters, bringing the perihelia of Oort cloud comets into the planetary region.

Volk 2013
The scattered disk is named for the mechanism that sculpts its dynamical structure: gravitational scattering due to close encounters with Neptune. The name originates from the work of Duncan and Levison (1997) who described the ‘scattered comet disk’ that resulted from their numerical simulations of massless test particles encountering Neptune.

The outer edge of the scattered disk is somewhat fuzzy. Objects scattered out to very large heliocentric distances become subject to significant orbital torques caused by galactic tides and the gravitational influence of passing stars. These external perturbations can increase the perihelion distance of an object thereby stopping the scattering process. Objects whose dynamics are strongly affected in this way are better described as being part of the Oort cloud.

In addition to the requirement of a > 50 AU, an object must have a perihelion distance greater than 33 AU to be classified as a member of the scattered disk. The use of q > 33 AU rather than q > 30 AU (the semimajor axis of Neptune’s orbit) to define SDOs is suggested by the results of Tiscareno and Malhotra (2003); their simulations of the planet-crossing Centaur population indicate that there is some overlap between the phase spaces of the Centaurs and the SDOs, but the relatively short-lived Centaurs rarely cross the q ≈ 33 AU boundary.

Semimajor axis (orange line) and perihelion distance (black line) vs. time for a typical scattered disk object in a numerical simulation. Repeated gravitational interactions with Neptune when the KBO is at perihelion (in the range 32-34 AU) cause the object’s semimajor axis to increase in a random walk fashion from its initial value of a ∼ 100 AU to a > 500 AU over the course of several hundred Myr.

At 41 AU, near the inner boundary of the classical Kuiper belt, there is also the secular ν8 resonance. The ν8 resonance destabilizes low-inclination orbits on very short timescales (Morbidelli et al. 1995; Kuchner et al. 2002); Figure 1.5 shows that there are no KBOs with i. 10◦ with semimajor axes in the range 40-42 AU. The outer boundary of the CKB is set by the location of the 2:1 MMR with Neptune at 47.78 AU; objects near but not in the 2:1 tend to be perturbed onto unstable orbits, and there is an observationally confirmed dearth of objects on low-eccentricity, non-scattering orbits exterior to this resonance

The RKBOs make up a substantial portion of the Kuiper belt. Some estimates put the population of just the 3:2 MMR at 10-15% of the classical Kuiper belt’s population

numerically integrated the orbits of 53 observed Centaurs and found that their median dynamical lifetime was only 9 Myr.

The fact that there are two distinct peaks in the inclination distribution of the CKBOs (discussed further in Chapters 2 and 5) indicates that the CKBOs might actually be comprised of two overlapping populations: a primordial low-i, low-e population (the ‘cold’ CKBOs), and a dynamically excited, high-e, high-i population (the ‘hot’ CKBOs) (Kavelaars et al. 2008); hints of this dynamical division can be seen in Figures 1.4 and 1.5.

Several studies have attempted to explain the origin of the bimodal inclination distribution. Kuchner et al. (2002) investigated the inclination-dependence of the long-term dynamical stability of Kuiper belt objects by performing numerical integrations of test particles with semimajor axes spread from 41 to 47 AU and uniform inclinations up to ∼ 30◦ . They found that in the inner part of the Kuiper belt, secular resonances systematically destabilize low-i test particles, resulting in an inclination distribution skewed toward higher i; however, they did not find any mechanisms that could raise the inclinations of an initially low-i population to values as large as 30, which have been observed in the classical Kuiper belt. Gomes (2003) 30 investigated how the outward migration of Neptune proposed by Malhotra (1993, 1995) could scatter objects from ∼ 25 AU onto high-i orbits in what is now the classical Kuiper belt region. This study suggests that the high-i population formed closer to the Sun and was emplaced in the classical Kuiper belt during planetary migration, whereas the low-e, low-i part of the classical Kuiper belt represents a primordial, relatively undisturbed population. Levison et al. (2008a) suggest that the entire Kuiper belt was emplaced during planet migration and that the ‘cold’ and ‘hot’ CKBOs represent populations captured at different times in the migration process and from different locations in the original disk (with the ‘cold’ CKBOs coming from larger heliocentric distances than the ‘hot’ CKBOs).

interestingly, the Centaurs have a bimodal color distribution (Tegler et al. 2008) that shows hints of an inclination dependence, although new studies indicate that this could instead just be a size-dependent effect (Fraser and Brown 2012; Peixinho et al. 2012). There have also been correlations proposed between inclination and other physical properties such as size, albedo, and binarity

The probability of detecting an object in the Kuiper belt is largely dependent on how bright that object is and on where it is in the sky compared to a survey’s pointing history. These two factors are fairly straightforward to account for because they are influenced only by the object’s orbit and intrinsic brightness (absolute magnitude), but other, more subtle biases are also present in the observed data set. One such bias occurs when an incorrect or poorly determined orbit leads to an inability to track and recover a newly discovered object; if orbit fitting procedures preferentially yield poor fits for certain types of orbits, those types of orbits will be under-represented in the set of recovered objects (Jones et al. 2010). It is not really feasible to remove such biases after the fact (Jones et al. 2010), so the debiasing procedures I outline below only account for biases based on brightness and sky position.

For example, Pluto is in both the 3:2 mean motion resonance and the Kozai resonance. The latter causes Pluto’s argument of perihelion to librate around 90 degrees. Physically, this means that the location of Pluto’s perihelion librates around its maximum excursion above the ecliptic plane. This phenomenon adds to the bias against detecting such objects because they are furthest from the ecliptic plane when they are brightest.

Brown and Batygin, 2018
Eventually, the planets encounter a low-order mean motion resonance, which results in a transient period of instability. During this period, the ice giants scatter outwards and settle roughly onto their current semi-major axes but with high eccentricities (Tsiganis et al. 2005; Thommes et al. 2008). Neptune’s excited eccentricity gives rise to a chaotic sea between its exterior 3:2 and 2:1 mean motion resonances (MMRs), allowing planetesimals to random-walk into the “classical“ region (Levison et al. 2008). Subsequently, as the planets circularize due to dynamical friction (Stewart & Wetherill 1988), the scattered and resonant populations of the Kuiper belt are sculpted. An outstanding problem within the Nice model lies in the formation of the cold classical population of the Kuiper belt, which is the central theme of this study

When Neptune scatters planetesimals, it tends to pump up their inclinations to tens of degrees. Yet the cold population resides on nearly co-planar orbits, with inclinations not exceeding ∼ 5 deg (Brown 2001; Gladman et al. 2008). The eccentricities of the cold population, on average, also tend to be diminished in comparison with the hot population, but the division there is not as apparent.

low-eccentricity objects progressively disappear beyond 45AU.

cold classical KBOs readily stand out as clump of exclusively red material (Trujillo & Brown 2002; Lykawka & Mukai 2005). In a similar manner, the size distribution of the cold population differs significantly from that of the hot classical population (Fraser et al. 2010). Finally, the fraction of binaries present in the cold population is uniquely large

Within the context of a smooth migration scenario (Malhotra 1995; MurrayClay & Chiang 2005; Hahn & Malhotra 2005), a primordially cold population can in principle escape dynamical excitation. However, other drawbacks of the smooth migration scenario, such as the inability to reproduce secular architecture of the planets and difficulties in forming the hot classical belt, render it unlikely

In order for a primordially cold population of KBOs to maintain an unexcited state, the average apsidal precession and nodal recession rates of Neptune during the transient phase of instability must have been considerably faster than what is observed in today’s solar system. Simultaneously, successful formation of the wedge (see Figure 1) requires that the apsidal precession rate drops by a factor of a few for a short period of time.

Fraser 2018
∼8% albedo, and retrograde orbit (Johnson & Lunine 2005). Orbits such as Phoebe’s are a natural bi-product of capture during the early reorganization of the gas-giants, which was also responsible for the dispersal of the proto-planetesimal disk (Nesvorný et al. 2007), implying that Phoebe broadly shares the same primordial planetesimal population as the dynamically excited Kuiper Belt Objects (KBOs; Levison et al. 2008). Admittedly, Phoebe’s density of 1.6 g cm−3 is roughly a factor of two higher than the typical densities of similarly sized KBOs (see for example Grundy et al. 2015).

a roughly spherical body, with a collisionally evolved surface possessing numerous large impact basins

The regions around gas giants are the most collision heavy in the solar system, so phoebe's surface may be atypical

water, co2 and iron-rich silicates

In particular, we find that Phoebe’s primordial surface was likely water poor. The large basin-forming impacts that Phoebe has undergone are responsible for enhancing the surface water content through dredgeup of water-rich subsurface material.

This implies that large impacts may be the source of the water–ice variations seen from KBO to KBO; the KBOs that exhibit the deepest water–ice absorptions are those that have undergone the most collisional bombardment.

The clear concentration of water in and around Phoebe’s two large impact basins argues that the impacts that formed those basins have modified the water distribution, enhancing water absorption on Phoebe’s surface. The positive correlation of depth and water absorption suggests a plausible scenario that the early Phoebe possessed a water-poor surface, with richer subsurface layers.

The broad range of water–ice absorptions exhibited by KBOs is broadly compatible with the variation in absorptions across Phoebe’s surface.

Phoebe’s surface exhibits the same range (F139m–F153m) color as do small KBOs. In particular, the color of the waterrich and water-poor spectral types match the colors of the bluest and reddest KBOs, respectively. Broadly, this implies that KBOs exhibit a range of water–ice concentrations similar to that observed on Phoebe. If Phoebe and the dynamically excited KBOs share the same primordial origins, it seems plausible that large basin-forming impacts could be responsible for enhancing the water–ice concentrations on KBOs like has occurred on Phoebe.

This idea would imply that KBOs with the highest water–ice concentrations are those that experienced the highest levels of collisional dredge up. KBOs with the lowest water–ice concentrations possess old surfaces that have undergone little to no collisional dredge up.

What ever organics are responsible for the red optical colors of KBOs, it is clear this material does not exist in any appreciable quantities on Phoebe’s surface. The heavy collisional bombardment Phoebe has experienced in the Saturnian environment may be responsible for the removal of this material. It has been observed that some centaurs lose their red coloring and transition to purely neutral surfaces at a similar point to when they dynamically transitioned from the centaur region to the Jupiter family comet region