When the moon goes splat

SMALL PRINT:IF YOU ARE A space fan, the last week or so has offered plenty to keep your brain cells tingling, including meteor showers and possible liquid on Mars. But did you hear the one about the moon going splat? Earth may have once had two moons which collided and merged, resulting in the farside highlands of the single moon that orbits our planet now.

That’s a scenario outlined in a letter to the journal Nature, which describes how simulations of that slow collision result in the smaller moon forming an “accretionary pile” rather than a crater.

And if moon-splatting theories weren’t enough to be getting on with, how about liquid water on Mars? Analysis of images from the surface of the red planet taken by the Mars Reconnaissance Orbiter describes intriguing features: dark streaks or tendrils that appear on some steep slopes in warmer periods and fade in winter.

There is already evidence of water on Mars in the form of ice, but this finding hints at a more fluid variety: “Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood,” write the study authors in Science.

Meanwhile, also on Mars, the rover Opportunity has been inching towards the Endeavour crater and has beamed back images from close to the rim.

At around 14 miles (22 km) in diameter, Endeavour is no meagre pothole, and is more than 25 times wider than Victoria crater, an earlier stop that Opportunity examined for two years. Closer to home, keep your eyes peeled at night for the annual Perseid meteor shower, which should peak this week.

Tsunami slices ice-shelf

WHILE THE MARCH earthquake and tsunami devastated parts of Japan, the tsunami had a physical impact much further afield, according to a study that tracked how it created icebergs in Antarctica, thousands of miles away.

Using satellite images, researchers observed icebergs “calving” or breaking off the Sulzberger Shelf with the arrival of the tsunami’s swell.

Data from the European Space Agency’s Envistat satellite revealed two large icebergs that had broken away, the biggest being around the size of Manhattan.

“The Honshu tsunami of 11 March 2011 traversed the Pacific Ocean in 18 hours where it impinged on the Sulzberger Ice Shelf, resulting in the calving of 125sq km of ice from a shelf front that had previously been stable for 46 years,” write the authors in the Journal of Glaciology. The conditions of the ice shelf and the sea-ice conditions immediately adjacent to the ice-shelf front may have helped the tsunami to trigger the breakup, they note.

Researcher Kelly Brunt describes on NASA’s website how they went looking for the impact. “In the past we’ve had calving events where we’ve looked for the source,” she says, but notes that this time the approach was turned on its head. “We knew right away this was one of the biggest events in recent history – we knew there would be enough swell. And this time we had a source.”