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.

LCROSS: is Moon's water due to comet impacts?

This image shows the plume that was raised when the LCROSS booster rocket struck the Moon in a region that is permanently shadowed from the Sun. The mission's goal is to search for the water-ice that might be frozen in these shadowed regions, since such ice would be a valued resource for any astronauts that might return to the Moon.

There are two likely sources for this water-ice. One is the solar wind, which can implant hydrogen into the lunar soil, which would then combine with the oxygen in soil to make water. Another source is comet impacts, which can deposit water as well as other volatiles that can then freeze out in these permanently shadowed regions. Since the spectra collected by LCROSS also reveals other volatiles, such as methane, ethanol, ammonia and carbon dioxide, all of which are known to exist in comets, cometary impacts are now a favoured theory for depositing water on the Moon.

Recent impacts on Mars exposes subsurface ice

The Mars Reconnaissance Orbiter (MRO) took these images of a 6m crater on Mars in October 2008 (left) and again in January 2009; see this press release for more details. This crater is absent from images acquired in 2007, so it must be due to a relatively recent impact. Note also the bright material in the crater that fades over time. This is to be expected if this were subsurface ice that was suddenly exposed to the surface. Water ice is not stable at the surface of Mars, and will sublimate (vaporize) over time. The MRO spacecraft has discovered several new craters where fresh ice appears to fade over time. This particular crater has a latitude of 43 degrees, which indicates that subsurface ice on Mars extends all the way from from the poles to Mars' mid-latitudes.