Shortly after the Moon formed, an asteroid smacked into its southern hemisphere and gouged out a truly enormous crater, the South Pole-Aitken basin, almost 1,500 miles across and more than five miles deep.

"This is the biggest, deepest crater on the Moon -- an abyss that could engulf the United States from the East Coast through Texas," said Noah Petro of NASA's Goddard Space Flight Center in Greenbelt, Md. The impact punched into the layers of the lunar crust, scattering that material across the Moon and into space. The tremendous heat of the impact also melted part of the floor of the crater, turning it into a sea of molten rock.

Planetary scientists have been puzzling for years over the honeycomb patterns and flat valleys with squiggly edges evident in radar images of Saturn's moon Titan.

Now, working with a "volunteer researcher" who has put his own spin on data from NASA's Cassini spacecraft, they have found some recognizable analogies to a type of spectacular terrain on Earth known as karst topography.

Flowing lava can carve or build paths very much like the riverbeds and canyons etched by water, and this probably explains at least one of the meandering channels on the surface of Mars.

These results were presented this morning at the 41st Lunar and Planetary Science Conference by Jacob Bleacher at NASA's Goddard Space Flight Center, Greenbelt, Md. Whether channels on Mars were formed by water or by lava has been debated for years, and the outcome is thought to influence the likelihood of finding life there.

Keeping an infrared telescope at very cold operating temperatures isn't an option, it's an absolute necessity. For the James Webb Space Telescope to see the traces of infrared light generated by stars and galaxies billions of light years away, it must be kept at cryogenic temperatures of under 50 Kelvin (-370°F).

Otherwise, sunlight would warm the telescope and this heat from the telescope itself will swamp the very faint astronomical signals, effectively blinding the telescope's eye. The job of the huge, five-layer sunshield is to keep that from happening.

ESA's Herschel Space Observatory has revealed the chemical fingerprints of potential life-enabling organic molecules in the Orion Nebula, a nearby stellar nursery in our Milky Way galaxy.

This detailed spectrum, obtained with the Heterodyne Instrument for the Far Infrared (HIFI) - one of Herschel's three innovative instruments - demonstrates the gold mine of information that Herschel-HIFI will provide on how organic molecules form in space.

New studies of ripples and dunes shaped by the winds on Mars testify to variability on that planet, identifying at least one place where ripples are actively migrating and another where the ripples have been stationary for 100,000 years or more.

Patterns of dunes and the smaller ripples present some of the more visually striking landforms photographed by cameras orbiting Mars. Investigations of whether they are moving go back more than a decade.

In general, galaxies can be thought of as "social" -- hanging out in groups and frequently interacting.

However, this recent Hubble Space Telescope image highlights how some galaxies appear to be hungry loners. These cosmic oddities have set astronomers on the "case of the missing neighbour galaxies".

New observations from NASA's Chandra X-ray Observatory provide evidence for powerful winds blowing away from the vicinity of a supermassive black hole in a nearby galaxy. This discovery indicates that "average" supermassive black holes may play an important role in the evolution of the galaxies in which they reside.

For years, astronomers have known that a supermassive black hole grows in parallel with its host galaxy. And, it has long been suspected that material blown away from a black hole - as opposed to the fraction of material that falls into it -- alters the evolution of its host galaxy.

NASA's newest Mars orbiter, completing its fourth year at the Red Planet this week, has just passed a data-volume milestone unimaginable a generation ago and still difficult to fathom: 100 terabits.

That 100 trillion bits of information is more data than in 35 hours of uncompressed high-definition video. It's also more than three times the amount of data from all other deep-space missions combined -- not just the ones to Mars, but every mission that has flown past the orbit of Earth's moon.

Extensive radar mapping of the middle-latitude region of northern Mars shows that thick masses of buried ice are quite common beneath protective coverings of rubble.

The ability of NASA's Mars Reconnaissance Orbiter to continue charting the locations of these hidden glaciers and ice-filled valleys -- first confirmed by radar two years ago -- adds clues about how these deposits may have been left as remnants when regional ice sheets retreated.

One of the pleasures of perusing ancient maps is locating regions so poorly explored that mapmakers warned of dragons and sea monsters. Now, astronomers using NASA's Fermi Gamma-ray Space Telescope find themselves in the same situation as cartographers of old.

A new study of the ever-present fog of gamma rays from sources outside our galaxy shows that less than a third of the emission arises from what astronomers once considered the most likely suspects -- black-hole-powered jets from active galaxies.

Using data from a NASA radar that flew aboard India's Chandrayaan-1 spacecraft, scientists have detected ice deposits near the moon's north pole. NASA's Mini-SAR instrument, a lightweight, synthetic aperture radar, found more than 40 small craters with water ice.

The craters range in size from 1 to 9 miles (2 to15 km) in diameter. Although the total amount of ice depends on its thickness in each crater, it's estimated there could be at least 1.3 trillion pounds (600 million metric tons) of water ice.

NASA's Phoenix Mars Lander showed no sign during February that it has revived itself after the northern Mars winter. NASA's Mars Odyssey orbiter will check again in early April.

The solar-powered Phoenix lander operated for two months longer than its planned three-month mission in the Martian arctic in 2008. It was not designed to withstand winter conditions.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• DTM: Channels from Hale Crater
  Geologists who study Earth's surface have several advantages over those who study other planets: they can often walk up to the units they are interested in, see them up close, touch them, test samples of them in laboratories -- in short, they generally have much greater access to their research areas than scientists who study other planets.
• A Field of Secondary Craters
  This observation shows a secondary crater field, which form when material ejected from a larger impact event impacts the Martian surface.
• Central Deposits in Pasteur Crater
  This observation shows a portion of the central sedimentary deposits in Pasteur Crater.
• Slope Streaks in Acheron Fossae
  This observation shows a portion of the wall (light-toned material) and floor of a trough in the Acheron Fossae region of Mars.
• Oudemans Crater Central Uplift: A Sample of Well-Preserved Layering
  This HiRISE image covers a portion of the central uplift of the 120 kilometer diameter Oudemans Crater.
• Candidate Landing Site in NE Syrtis Major
  This image lies on the eastern edge of a candidate landing site in the northeastern part of Syrtis Major, a huge shield volcano, and near the northwestern rim of Isidis Planitia, a giant impact basin.
• Craters on an Ice-Rich Debris Apron
  This observation shows a swath of a debris apron east of Hellas Basin. Features like this are often found surrounding isolated mountains in this area.
• Northern Meridiani Etched Terrain and Hematite Plains Contact
  This observation shows the contact between the hematite bearing plains and etched terrain in northern Meridiani Planum.
• Gullies and... Gullies? in Terra Sirenum
  This observation shows part of an unnamed crater, itself located inside the much larger Newton Crater, in Terra Sirenum.
• Dunes and Inverted Craters in Arabia Terra
  This image shows dark sand dunes and inverted craters in the Arabia Terra region of Mars.
• Monitoring of Polar Avalanche Region
  This HiRISE image shows the scarp that demarcates the boundary between layered deposits covering the north polar region and the lower surrounding terrain, which includes sand dunes.

The following new images taken by the Imaging Science Subsystem (ISS) on the Cassini spacecraft are now available:

• Balancing It Out (Released 22 February 2010)
  Two small but stately moons appear above and below the rings on the left of this image, serving to visually offset the dominance of Saturn on the picture's right.
• Shadow from the Gap (Released 23 February 2010)
  Orbiting in the Encke Gap of Saturn's A ring, the moon Pan casts a shadow on the ring in this image taken about six months after the planet's August 2009 equinox.
• Oblate Iapetus (Released 24 February 2010)
  The oblate shape of the moon Iapetus is particularly noticeable in this portrait.
• Saturn Bright Through Rings (Released 25 February 2010)
  The limb of Saturn appears bright as the Cassini spacecraft peers through several of the planet's rings.
• Hidden Janus (Released 26 February 2010)
  The small moon Janus is almost hidden between the planet's rings and the larger moon Rhea.