steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
Hell on Earth: NASA’s Toxic Venus Test Chamber

Making a spacecraft to land on Venus (as opposed to orbit it) is really difficult, because the environment on Venus is so extreme. The surface temperature is extremely hot (hot enough to melt lead), the atmospheric pressure is 90 times that on earth, and the atmosphere contains corrosive gases. Because of this, none of the few spacecraft that have successfully landed on Venus so far have been active for more than a few hours.

So NASA is making a Venus environment simulation oven to do testing for possible future missions to Venus, so that they can determine what will or won't last without sending it to the planet and then finding it doesn't work very well.

The chamber could also be used for simulating some other non-Earth environments, such as Jupiter's outer atmosphere.

On an unrelated note, yesterday (at least from my time zone), January 9th, was the anniversary of the death in 1848 of astronomer Caroline Lucretia Herschel. She "found three nebulae and eight comets. In 1787, King George III gave Caroline a salary of 50 pounds per year as assistant to [her brother] William. She published the Index to Flamsteed's Observations of the Fixed Stars and a list of his mistakes in 1797." Caroline's brother William Herschel discovered Uranus.
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
On Friday there were three press releases:
Number one: Subtly Shaded Map of Moon Reveals Titanium Treasure Troves. Certain parts of the moon have surprisingly large amounts of titanium. Maps of the moon in visible and ultraviolet light show which parts of the moon are high in titanium. We don't really understand why the moon has as much titanium as it does, but it does give us some clues about the history of the moon. These visible and ultraviolet light also show some interesting things about space weathering.

Number two: The cause of asteroid Scheila’s outburst. In 2010, the asteroid Scheila started showing comet-like features, including a tail. Material presented at the conference provides evidence that this was caused by an impact from a much smaller asteroid (Scheila is about 110 kilometres in diameter; the impactor is calculated to have been between 60 and 180 metres in diameter, so about a thousandth of Scheila's diameter.)

Number three: Almahata Sitta meteorites come from triple asteroid mash-up. On Oct. 7, 2008, three years to the day before the date of the press release, for the very first time an asteroid which had been detected in space and predicted to hit Earth actually did so. It landed in the Nubian Desert in Sudan, and more than 600 fragments have been retrieved. They're named Almahata Sitta. The varying composition of the fragments suggests that they belonged to a parent body that was created by relatively low-speed collisions between asteroids of different types.

And here's Emily Lakdawalla's post on Day 5 of the conference. Some of the things she talks about: the great storm on Saturn; Mars's moon Phobos is probably a rubble pile; there's good evidence that the grooves on Phobos are caused by stuff ejected by impacts on Mars; a more precise calculation than previously of the mass (and thus density) of the asteroid Lutetia; the asteroids Lutetia and Steins both have more recent large craters than we'd predict, which suggests that we may be underestimating the number of small asteroids.

Now for other bits and pieces and news stories written up by people besides me, from any part of the conference, not just the last day:

Emily Lakdawalla's notes on NASA's Planetary Night, "in which representatives from NASA's Science Mission Directorate speak to the people whose missions and research they fund about their accomplishments and the political and funding climate for the coming years". Most of the news is pretty discouraging, but there's one bright bit: that the production of Plutonium-238 is going to be restarted, so there will be a reliable power source for missions that can't use solar power.

A Whole New World at the Edge of the Solar System. About Kuiper Belt Objects, what we can learn from light curves, what they say about Haumea, what a contact binary is, and, in culmination, how the light curve of a certain Kuiper Belt Object shows that it's a contact binary, and why changes in that light curve over the past few years give an indication that such contact binaries may be common among Kuiper Belt Objects.

The Revelations of Planets' Shadows. About what we've learnt about Makemake and Quaoar from them occulting stars.

Did Earth's oceans come from comets? The water in previously observed comets has about twice as much deuterium (hydrogen with a proton and a neutron rather than just a proton) as Earth's water does. This was a problem for accounts of the origin of Earth's water that said it came from comets. But recent observations of comet Hartley 2 show that it has almost exactly the same amount of deuterium as Earth's water. It was formed in a different part of the solar system from the comets that were found to have more deuterium than Earth's water, and this probably explains why it's different from them.

When Minor Planets Ceres and Vesta Rock Earth Into Chaos. The two largest asteroids, Ceres (which is a dwarf planet as well as an asteroid) and Vesta, gravitationally affect each other; they also gravitationally affect earth, so that we can't reliably predict Earth's orbit farther into the future than about 60 million years; we also can't reconstruct the details of Earth's orbit farther back than about 60 million years.

Did Mercury and Uranus Have a Rough Youth After All? About the early history of Mercury and Uranus, and how many major impacts they received; for Mercury, it's about the question of how it got its present density while retaining relatively volatile elements like sulfur and potassium, while for Uranus it's about the idea that several major impacts gave it its present large tilt.

Pea shooter theory aims to build solar system. About a new tentative hypothesis about how the planets of the solar system formed - that rather than forming in about the regions where we now find them, they all formed initially at roughly Earth's distance (well, at least the ones outwards of Earth) and made their way outwards to their present distances.

And finally, one thing I found on Twitter but not in the articles mentioned above. Again, don't take my extractions of stuff from Twitter too seriously.

Satellites of Mars
There was a talk arguing that Phobos and Deimos were created out of the debris from a large impact on Mars - the impact would have created a debris disc around Mars, which then accreted into Phobos and Deimos. This explains their orbits better than the idea that they're captured asteroids - their orbits are too circular and too much in the same plane to be captured asteroids. Mars's rotation rate also implies that Mars got a large impact, and there are several impact basins on Mars that are the right size to account for both the spin rate and the moon formation.

Twitter source:
[ profile] kat_volk
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
Three press releases today:
Number one: ESA finds that Venus has an ozone layer too. It was already known that Mars as well as Earth has an ozone layer. They found Venus's by analyzing the spectra of stars seen through the very outer edge of Venus's atmosphere.

Number two: The Secrets of Asteroid Minerva and its Two Moons. Moons let scientists figure out Minerva's mass. They figured out its diameter from a combination of watching it occult a star, and infrared measurements, both of which pointed to a diameter of about 156 km. This lets them calculate its density - about 1.9 grams per cubic centimeter; based on the density of what they think it's made of, that indicates that it must have about 30% empty space in its interior.

Number three: Series of bumps sent Uranus into its sideways spin. This is about a new hypothesis, not a new discovery. The previous standard account for Uranus being tilted on its side was that a single large impact had changed its orientation. The problem with that explanation has always been that it didn't explain why its moons orbit it in similarly tilted orbits. New computer simulation results show that this can be explained if Uranus was hit before the moons formed, while it was still surrounded by a protoplanetary disc out of which the moons later formed, and if it was tilted by two or more impacts, rather than by a single one.

And what I got from Twitter. As before, don't put too much confidence in it; I could very well have misinterpreted things or expanded them wrongly.

I'm not sure how much of this is new, but: Venus has lightning, and like on Earth, some days have more lightning than others, depending on the weather. The lightning rate on Venus is probably comparable to that on earth, about 100 flashes a second worldwide, but that's hard to prove.

Venus's cloud tops are generally 72 km above the surface, except at the poles where they're only 65 km up.

Global climate models for Earth aren't working for trying to understand Venus, which indicates that they might not be working right for Earth either. To understand Earth's climate, we have to understand Venus too.

Saturn's moons
One of the puzzles about Saturn's moon Iapetus is why it has a ridge running around its equator. One hypothesis has been that it used to be spinning faster, which made it more oblate (i.e., bigger around at the equator than at the poles) due to centrifugal effects, but its rotation slowed, so gravity made it more spherical than oblate, but the rearrangement process from more oblate to less oblate created an equatorial ridge. The problem with that is how exactly the spin change could have worked to create that result. The proposal now presented is that if Iapetus once had a satellite of its own, that might make it possible to reduce Iapetus's spin enough to create the ridge. (I don't know how a satellite would help that, though.)

It was discovered over a year ago that Mimas has a weird Pac-Man-shaped temperature pattern; there's a relatively warm area that looks like a Pac-Man shape on images, and relatively cold area on the leading hemisphere that looks like the inside of Pac-Man's mouth. News: The cold part of the leading hemisphere - the area inside Pac-Man's mouth - is correlated with an area in the leading hemisphere that is dark in UV light. Also, as of September 2011, a similar anomaly seems to have been observed on Tethys. (I think this means both the temperature pattern and the correlation with a UV-dark leading hemisphere area have been observed on Tethys, but I'm not sure about the second half.) There's a hypothesis, which still sounds quite tentative, that it might be caused by being bombarded by electrons, which somehow (not clear from Twitter) increase the thermal inertia of the moon's material. (Also not entirely clear to me whether the electrons are bombarding the warmer area or the colder area.)

The outer irregular satellites of Saturn that Cassini observes are so faint that if you were sitting on Cassini, you couldn't see them with the naked eye.

Other stuff
Almost all near-earth asteroids smaller than 60 metres diameter rotate really fast - in less than 2 hours.

Dust from collisions between irregular satellites of Jupiter might have left 100 metres of dust on Callisto and 20-30 metres of dust on Ganymede.

It sounds as if there was some interesting stuff about Europa, but not that I could contextualize well enough to pick out relevant tweets and expand on their significance as needed.

Good news: Jim Green, the Director of Planetary Science for NASA, says that production of Plutonium-238 will be restarted, so there will be a reliable power source for outer solar system missions.

Twitter sources:
[ profile] DrFunkySpoon
[ profile] kat_volk
[ profile] gsinfinite
[ profile] elakdawalla
[ profile] jeanlucmargot
jeweledeyes: Sailor Venus thinks you're a loser (Kowalski science)
[personal profile] jeweledeyes
More about possible fuel methods for Project Icarus: tapping into the "gas mines of Uranus"!



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