Streaks at Martian crater suggest a watery flow

This is the upper edge of the Newton crater on Mars, imaged my the Mars Reconnaissance Orbiter (MRO). The dark streaks extending downslope are very interesting; they are only seen in spring and summer, and fade away during the colder seasons. These streaks might be due to a flow of subsurface water that is likely a salty brine due to long-term contact with the martian rocks. Salt lowers the freezing point, which might allow subsurface ice to melt and seep down the crater's slope. This might be the cause for the seasonal stains that are seen in the crater's soil. Additional details can be found at the MRO website, including this nice movie of streaks forming and then fading. If these streaks are in fact watery seeps, they will be of great biological interest because wet soil will be a natural place to look for microbial life on Mars.

Martian gullies at crater's edge

Gullies are often spotted in sloped terrain on Mars, like the ones seen here at the edge of Hale crater on Mars. This image was acquired by the Mars Reconnaissance Orbiter August 3, 2009; that spacecraft has been observing Mars since March 2006. Martian gullies are of great interest, since their dendritic appearance suggests that groundwater might be seeping out and flowing downhill. However, after many years of study, it is still unclear whether wet or dry processes are responsible for sculpting these gullies. Dry processes include boulders or avalanches that might carve out these gullies as rocks and gravel tumble downhill. Also keep in mind that the martian surface is too cold for liquid water to exist there. Nonetheless, any groundwater would absorb salts from the surrounding rock, which might lower its freezing point enough to exist in liquid form. And where there is liquid water, there is also the possibility for microbial life. For more details, see this press release.

Ingredients for prebiotic life found in comet

The Stardust spacecraft encountered comet Wild 2 on January 2, 2004, and collected samples of the comet's coma and tail. Those samples parachuted to Earth on January 15, 2006, and have been studied in labs ever since. From these samples, Jamie Elsila at NASA/Goddard reports the first ever detection of glycine in a comet. Glycine is a common amino acid, which when combined with others can build proteins, which are important building blocks in the chemistry of life. The detection of glycine in comet Wild 2 strengthens the argument that comet impacts on the early Earth provided the prebiotic chemistry that ultimately allowed life to begin on Earth. However, critics of this cometary-delivery theory would argue that comet impacts are far too fiery and energetic to deposit complex organic molecules on Earth whole and unscathed. Regardless, this interesting finding highlights the value of sample-return missions, which can provide valuable insight into composition of ancient and primitive bodies, like as comets and asteroids, that are the primordial building blocks of the planets. See this press release for more details.