Spacecraft's Double-Take Reveals Changes on Mars

Here today, gone tomorrow; a bright layer of frost lining a crater wall is vanquished by the springtime sun — and seen by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter high overhead.

The image above shows a 1 kilometer (0.6 mile) wide crater in Mars’ southern hemisphere, its northern wall and coated with frozen carbon dioxide, what we call “dry ice.” HiRISE captured the view on June 28, 2014 from a distance of 248.8 km (155.5 miles), during what was late southern winter on Mars.

A few months later during the southern spring, the same region was imaged with HiRISE. Lo and behold the frost was gone from the crater wall and surrounding ejecta blanket, having sublimated back into the atmosphere.

Images like these demonstrate the value of long-term planetary missions like MRO. A single “snapshot” of a region on Mars — or Saturn, or Titan, or Pluto, or wherever — doesn’t give us the whole picture of what may happen there over the course of a year.

According to Livio Tornabene of the HiRISE team, “Repeat coverage actually serves a special purpose, such as detecting seasonal changes (frost deposition and sublimation) and temporal changes (dust devil tracks and avalanches.) These repeat images also give us a ‘sneak peek’ of future pictures to determine any differences.”

A year on Mars is 687 Earth days long, a month and a half shy of two Earth years. By this October the crater seen above will once again turn white with frost as southern winter sets in and the carbon dioxide in Mars’ atmosphere freezes down onto the colder, south-facing surfaces.

The HiRISE (High Resolution Imaging Science Experiment) instrument aboard MRO is managed by the University of Arizona and captures images of the surface of Mars in extraordinary detail. Its camera can resolve details down to about a meter in size from Mars orbit.

Read more at Discovery News