Caught in the act: an avalanche races down an escarpment on Mars.
Photo by: Nasa/JPL-Caltech/University of Arizona
The US National Aeronautics and Space Administration (Nasa) has just released this photograph of an avalanche in progress on the surface of Mars. The avalanche was caught by the HI-RISE imager on Nasa’s Mars Reconnaissance Orbiter (MRO) spacecraft.
The avalanche took place in Mars’ northern polar region in late May, during spring. With the rising temperatures, ice vaporises (Martian atmospheric pressures are too low to allow liquid water on the planet’s surface), destabilising ice blocks, which then break loose and slide down into the valley below. In the process they kick up lots of dust.
The cliff on which this avalanche occurred was about 500 m high. Also visible are layers on the surface of the Martian north polar region during spring.
HI-RISE is an acronym for High-Resolution Imaging Science Experiment. It operates in the visible and near-infrared wavelengths and is equipped with a telescopic lens. MRO has three other imagers, plus an imaging spectrometer, and an array of other experiments including a shallow ground-penetrating radar.
The spacecraft was launched in 2005 and arrived in Martian orbit in March 2006. It had the prime mission of researching the history of water on Mars. Its primary mission was meant to end in December 2010, but the MRO is still going strong, its mission having been extended several times.
The spacecraft is powered by solar panels and has no less than 20 thrusters, of which only eight are used (along with reaction wheels) to control the spacecraft in Martian orbit. (The other 12 thrusters were used for course corrections during interplanetary cruise and for deceleration into Martian orbit.) The MRO also acts as a communication relay station for Nasa landers and rovers on the Martian surface.