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:
[twitter.com profile] kat_volk
steorra: Jupiter's moon Europa (europa)
[personal profile] steorra
First, stuff written up by other people.

It looks like there's only one press release today, on MESSENGER at Mercury (related graphics here). Among other things, Mercury's magnetic field is weird - it's shifted north by about 20% of Mercury's radius, so the field is stronger in the northern hemisphere than in the southern hemisphere.

Emily Lakdawalla's daily summary is also all about MESSENGER's results at Mercury, and goes into some stuff that didn't make it into the press release, such as that Mercury seems to be made of darker stuff than the Moon, and that Mercury has a smaller range of heights between highest and lowest than the Moon or Mars. (Mercury: about 10 km; Moon: about 20 km; Mars: about 30 km).

Stuff from Twitter; again, take with many grains of salt, because I don't know what distortions I may have introduced.
Mercury
Elaboration on the weird magnetic field: the magnetic field's axis is aligned with the rotational axis, to within 3 degrees; but the magnetic field itself is shifted north along that axis.
Mercury's crust is about 50-80 km thick at the equator, 20-40 km thick at the north pole.
Mercury's surface is low in titanium and iron, but has lots of sulfur.

Enceladus
The state of relaxation of craters in the northern hemisphere of Enceladus indicates that even heavily cratered parts of Enceladus (i.e., the parts where craters haven't been overrun by geological activity) indicates that even those regions have to have had a (relatively) high heat flux in the past.

Earth's Moon
Ancient craters and relatively recent craters have different size distributions. The size distribution of ancient craters looks like what you'd get if you took stuff indiscriminately from the main asteroid belt and smashed it into the Moon. The size distribution of more recent craters looks like the size distribution of near-earth objects, which are removed from the main asteroid belt by a process that's affected by size, the Yarkovsky effect.

Other stuff
Saturn's moon Aegaeon is really really elongated: 1.4 x 0.5 x 0.4 km.

Twitter sources:
[twitter.com profile] spacemandave
[twitter.com profile] DrFunkySpoon
[twitter.com profile] elakdawalla
[twitter.com profile] asrivkin

Profile

Astronomy

April 2017

S M T W T F S
      1
2345 6 78
9101112131415
16171819202122
2324252627 2829
30      

Syndicate

RSS Atom

Most Popular Tags

Style Credit

Expand Cut Tags

No cut tags
Page generated Sep. 21st, 2017 11:14 pm
Powered by Dreamwidth Studios