Astro News: 3rd December 2011

In the Universe this week: Mixed news for Mars missions, Mercury is weird, and the Voyager spacecraft see star formation.

The Voyagers see star formation

When we look at other galaxies, a tell-tale sign that new stars are being created is the presence of “Lyman-alpha emission”. This is a particular kind of energetic ultraviolet light that is emitted by the hot, young stars that are the brightest products of star formation. When we try to detect Lyman-alpha from star forming regions in our own galaxy, however, ultraviolet radiation from the Sun swamps any signal that we might hope to measure. This is a shame, because Lyman-alpha measurements would be a useful test of our theories of star formation. Enter the Voyager spacecraft, which visited Jupiter, Saturn, Neptune and Uranus in the late 70s/early 80s, and have been hurtling outwards into interstellar space ever since. The two probes are nearing the boundary of the Solar System, and are now so far from the Sun that a successful measurement of the Lyman-alpha emission from our own galaxy can be made. Despite the distance, the solar emission still accounts for 90% of the detected signal!

Curiosity Mars rover blasts off; Phobos-Grunt stays behind

There's both good and bad news for would-be explorers of the Red Planet this week. NASA's latest rover, Curiosity, was successfully launched into space from Cape Canaveral on Saturday, and is expected to reach Mars in August next year. Curiosity is a nuclear-powered behemoth, some five times heavier than any previous Mars rover, and packed to the brim with instruments designed to extract and analyse samples of Martian rock. It’s heading for a site which hosts what appears to be an “alluvial fan”, a geological formation that, on Earth, would be created by fast-flowing water. The hope is that samples taken from this location will provide further clues as to the nature of ancient water flows on the planet. And if there was water, maybe conditions were right for life at some point too?

Sadly, Russia’s Phobos-Grunt mission, which failed to launch correctly earlier this month, has now missed any opportunity to recover from its problems and continue on its way. So, while Curiosity is happily tweeting away, Phobos-Grunt is resigned to a fiery end when it crashes back to Earth at the end of the year.

[url=http://www.nasa.gov/mission_pages/messenger/media/Telecon20110929.html
]Mercury is a bit weird[/url]

The first batch of results from the MESSENGER Mercury orbiter have arrived, and they paint a slightly weirder picture of the Sun’s closest companion than we first expected. Mercury has a rather rough surface, pock-marked with craters and other impact features. Large “floods” of lava seem to have shaped sizable regions of its surface too; images show smooth plains containing “ghost craters” that have been filled-in with molten rock, leaving only an outline of their original shape. You might expect this volcanic activity to be associated with large asteroid impacts, since these are very energetic and can melt a lot of rock! But the MESSENGER results suggest that the lava floods have some another source, “independent of the largest cratering events”. This points to the surface and mantle of Mercury having been almost completely molten at some point around 4 billion years ago.

Image: JPL Archives/NASA