Planetary scientists had plenty of new results to present this week at the 44th annual meeting of the American Astronomical Society's Division for Planetary Sciences. Here are some of the highlights.
A UCLA duo reported October 15th that more than 85% of planetary systems are "flatter than pancakes." Julia Fang and Jean-Luc Margot created computer mockups of a diverse range of exoplanet systems in which the planets take less than 200 days to orbit their suns. Then they determined what these systems would look like to Kepler and compared the results to actual Kepler detections.
The team found that, in 85% of all cases, the planets' orbital inclinations were less than 3°, meaning that if you looked at the systems from the side, their thicknesses would be something between a crepe and a pancake (as determined by Margot's cooking trials). The flatness is similar to our own solar system and suggests that most planetary systems evolve undisturbed by major shakeups. Click to read Fang and Margot's research paper.
Earth's Eyes on Io
Researchers at NASA's SETI Institute have captured 40 snapshots of volcanic eruptions on Io, and all from the comfort of home. Earth-based telescopes have taken over the task of monitoring the Jovian satellite — the last spacecraft to fly by Io was New Horizons in 2007, and no future visits are planned. Equipped with adaptive optics, 8- to 10-meter telescopes can resolve details as small as 100 km (60 miles). Ground-based scopes have watched several fire fountains erupt over the years, but oddly enough, none since 2010: for the past two years, all has been quiescent on the Ionian front. Click to learn more about the new ground-based observations of Io.
Best-Ever Pix of Uranus
When Voyager 2 flew by Uranus in 1986, the planet offered little to see: just a deep, clear atmosphere of greenish blue "air." Since then Uranus has grown clouds and weather. In July astronomers at Keck Observatory on Mauna Kea obtain the most detail-rich images of Uranus ever taken, using adaptive optics and a variety of other techniques.
Uranus’s hydrogen-and-helium atmosphere contains substantial methane, which can freeze out and form white clouds. Some of the resulting weather systems "stay at fixed latitudes and undergo large variations in activity," says Larry Sromovsky (University of Wisconsin). "Others are seen to drift toward the planet's equator while undergoing great changes in size and shape." This complexity is puzzling because strength of sunlight at Uranus is only 1⁄900 that at Earth, and (unlike Neptune) the planet has no detectable energy coming from its interior. For details see this press release.
A New Way to Make the Moon
How did the Moon come to be? For nearly 30 years, planetary scientists have generally agreed that it's a consequence of something big (roughly Mars-size) having struck the very young Earth. Other hypotheses have been proposed, going back to the late 1800s, but only this "big splat" comes close to satisfying a wide array of physical and geochemical constraints — and one of the most stringent is the high angular momentum of the Earth-Moon system. To get it, it's been thought, the impactor must have dealt Earth a glancing blow.
But a nagging geochemical problem, dynamicists admit, is that a glancing blow leaves the Moon with too much impactor and too little proto-Earth. But new simulations by Matija Ćuk and Sarah Stewart (Harvard University) sidestep this dilemma by having the impactor make more of a direct hit on an Earth that was rotating in just 2 or 3 hours — whirling so rapidly that it was close to flying apart on its own. Find out more in a press release describing Ćuk and Stewart's work, which appears in full in the October 17th edition of Science Express.