Vesta's rugged surface

This image is a computerized rendering of what a hypothetical observer migth see when looking obliquely along the mountains and craters on the giant asteroid Vesta. Of course the Dawn spacecraft is in orbit about Vesta, and thus is always looking down upon the asteroid, so Dawn would never see anything like this. But Dawn has now collected enough measurements of Vesta surface topography to assemble a detailed computer model of the asteroid's surface. With that model, one can then calculate the view that any observer might see when looking in any direction about Vesta. Keep in mind that Vesta is only about 700 miles across, so the more distance mountains shown here would not be seen by that observer; they'd lie below the horizon and thus would be hidden. But that computerized view can be adjusted to remove the asteroid's curvature (ie, flatten the asteroid) while preserving its topography, as is seen here. See the Dawn website for more details about this computerized image of Vesta's rugged surface.

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.

Messenger's first image from Mercury orbit

The planet Mercury acquired its first artificial satellite on March 17, when the Messenger spacecraft went into orbit about the planet. Two weeks later, the spacecraft acquired its first image from Mercury orbit, with 75,000 more images to be acquired during the next year. See this press release for more details and a much larger image, or visit the Messenger website.

Rare elongated crater on Mars

ESA's Mars Express imaged this elongated crater on Mars. Note that most craters are circular, even when the impactor strikes the planet at a shallow angle. However a train of interplanetary debris can leave an elongated scar, which might account for the crater seen here. But accounting for the origin of that hypothetical debris train can be problematic---perhaps this is debris from a comet or asteroid that was tidally disrupted by Mars? Or perhaps this debris is from a tidally disrupted satellite that had spiraled inwards and onto the planet due to the martian tide. Although this might seem farfetched, this in fact will be the ultimate fact of the Martian satellite Phobos, which will eventually impact Mars in tens of million years, due to its slow orbital decay that is driven by the martian tidal forces. See the Mars Express website for more details.

Stardust sees impact site on comet Tempel 1

The stardust spacecraft flew by comet Tempel 1 last night, and acquired the close-up image of the surface that is seen on the left. Recall that this comet was first visited by the Deep Impact spacecraft in 2005, which shot that comet with a one-ton projectile; the high-res image on the left shows the impact site prior to the collision. One of Deep Impact's science goals was to observe the resulting crater, but the impact generated so much dust, the crater was never seen by Deep Impact. Fortunately, the Stardust spacecraft could maneuvered so that it would encounter comet Tempel 1 six years later. Stardust acquired the fuzzy low-res image on the right, which does indeed show the impact site, with a shallow 100m crater just inside the smaller circle. Note also that the impact obliterated the dark region that is seen at 10 o'clock along the yellow circle (left), in the pre-impact image. The Deep Impact crater has been observed at last!