Tuesday, May 26, 2009

Mars landers:
destroying the organics they were sent to find?

Even if there is no life present on Mars, that planet should have organic molecules on its surface, due to impact delivery by asteroids and comets, which are known to contain organic carbon-bearing molecules. However, organics have not been detected by any landers sent to look for these materials---not by the Viking landers, nor by the more recent Phoenix lander. Organics are detected by heating soil samples in an onboard oven, and looking for their signature in the gases released during heating.

However, Douglas Ming (Johnson Space Center) and colleagues note that the Martian surface contains perchlorate salt, which releases oxygen when heated. Ming's experiments also show that this released oxygen might then burn up any organics present in the soil samples. So if Ming's thinking is correct, this might explain why the Martian landers have not detected organics on Mars---their detection methods might have been burning up the organics that they seek. For more information, see this New Scientist article, as well as Ming's LPSC abstract.

Friday, May 22, 2009

Split Comet Schwassmann-Wachmann 3

Comet Schwassmann-Wachmann 3 broke up into several fragments in 1995. Its orbit period is 5.4 years, so came closest to the Sun again in 2001 and 2006. Bill Reach and colleagues used the Spitzer Space Telescope to observe this comet in infrared wavelengths in May 2006. The faint band connecting the fragments is a trail of debris that traces their orbit about the Sun. These astronomers detected 55 fragments along this comet's orbit, several of which are seen above. The color image of two brighter components show their dusty tails in red with a hint of green to show that CO2 gas is emitted from the sunward-facing parts of the comet nuclei. These fragments comae and tails are generated as the icy cometary nuclei warm and sublimate (evaporate) in the sunlight, whose weak pressure also sweeps the dust away in the anti-sunward direction. A preprint by Reach et al on these Spitzer observations is also available.

Friday, May 15, 2009

Shuttle transits the Sun

Space Shuttle Atlantis was photographed in silhouette against the Sun on May 13th by French astrophotographer Thierry Legault, while in Florida. The shuttle's transit across the Sun lasted only 0.8 seconds, and this picture was taken before the shuttle caught up with Hubble. See Legault's website for other other very nice astronomy pictures.

Wednesday, May 13, 2009

Girl who named Pluto dies at 90

Venetia Phair, UK, was 11 when Pluto was discovered by Clyde Tombaugh at the Lowell Observatory in 1930. Her grandfather, Falconer Madan, told her of the discovery, and discussed possible names for the new planet. ‘Why not call it Pluto?’, she suggested. Madan passed the suggestion on to friend Herbert Hall Turner, professor of astronomy at Oxford, who in turn telegraphed Lowell Observatory, which endorsed the suggestion. Venetia's grandfather gave her a five-pound note for her idea. Venetia died April 30 in her home in Banstead, England.

Monday, May 11, 2009

Shuttle mission to Hubble

Space shuttle Atlantis launched today, to service the Hubble Space Telescope for the forth and final time. Astronauts will replace several new cameras and
spectrographs (which will be used to measure the composition of stars, planets, galaxies, etc), and repair others. Astronauts will also replace one of two redundant devices that handle data, will replace Hubble's batteries, and will replace all of the HST's six gyroscopes (which orient the telescope), of which only half now work. One of three Fine Guidance Sensors--which also help point the telescope and are used to hunt for extra-solar planets--will also be replaced. A ring will also be attached to the telescope's backend, so that a rocket can at a later date be attached and used to deorbit Hubble at the end of its life. Hubble has been operating for 18 years, and has been one of the most productive telescopes ever. This servicing mission should extend its life for another 5+ years.

Thursday, May 7, 2009

Shadows at the edge of Saturn's B ring

This fascinating image is from the April 15 Astronomy Picture of the Day. The image was acquired by the Cassini spacecraft, which is in orbit about Saturn. The brighter part of this image is a close-up of the outer edge of Saturn's B ring, while the lower darker part shows the fainter ring material that orbits in the Cassini Division. Saturn is approaching equinox, which means that the Sun is near the ring plane, which also allows the satellite Mimas to cast its shadow on the ring plane (dark vertical streak).

Note also the dark `cookie bites' missing from the outer edge of the B ring. These seem to be shadows cast by something that lies right at the ring edge, possibly very large ring particles orbiting there. But note the bright ringlet that also appears at the B ring's outer edge; if that ringlet is puffy, or otherwise kinky in the vertical direction, then that ringlet might be casting these shadows. Also keep in mind that Mimas has a 2:1 resonance at the B ring's edge, which is where a ring particle orbits twice for every orbit of Mimas. So it is conceivable that resonance might be 'snowplowing' the B ring edge, with ring material also piling up in a vertically above and below the ring-plane as Mimas also shoves it radially inwards. If so, then this snowpiling might instead be responsible for these shadows.

NASA's 2010 budget

NASA announces its budget for fiscal year 2010. The table is from the budget summary, which shows how NASA spends its money. The 2010 budget is about $18 billion, with more than half spent on Exploration/Space Ops (eg, manned spaceflight), and almost a third on Science, with the rest spent on activities at various NASA centers (Johnson, Ames, etc). Of interest to me is the Planetary Science budget line, which stays flat until year 2011.

Wednesday, May 6, 2009

Image of planet orbiting Fomalhaut

This remarkable image shows the motion of the Jupiter-mass planet as it orbits the star Fomalhaut (see inset). This optical image was acquired by Paul Kalas (UC Berkeley) and colleagues using the Hubble Space Telescope. Interestingly, this star also harbors a dusty circumstellar debris disk. The planet orbits just inside a gap within this disk, and its gravity is responsible for keeping that gap clear of dust. Note also that the debris disk appears to resemble a ring, due to the disk's inner edge being illuminated by the central star. The dust in these debris disks is thought to be generated by collisions among unseen planetesimals (eg, asteroids or comets) that also probably orbit within this disk. The ellipse in this graphic has a radius of 30 AU (1 AU = Sun-Earth distance), which is the radius of Neptune's orbit. The radius of the disk's inner edge is about 140 AU, which is about 3 times larger than the size of our Solar System's Kuiper Belt, which is also a belt of comets orbiting just beyond Neptune.

Welcome to Solar System Watch!

First post...welcome! This blog is devoted to the latest astronomy news, with a special emphasis on planetary science, which is also my field of study. And if you are wondering who is doing the blogging here, please have a look at my profile.

The blog's title graphic is extracted from this image of Saturn that was acquired by the Cassini spacecraft on May 4, 2005. Here we are looking obliquely onto the dark side of the ring plane. Saturn was in winter when this image was acquired, so the Sun is south of the rings, which also cast shadows onto Saturn's northern hemisphere.