Mars sports highest clouds in the inner solar system: scientists

French scientists have discovered the highest clouds above the surface of any of the inner planets, using the SPICAM instrument aboard the European Space Agency's Mars Express, in orbit around the Red Planet.

For years, scientists believed that there were only clouds in the lower reaches of the Martian atmosphere. But upon further research, scientists from the Service d'Aeronomie in France found a layer of clouds at an altitude between 80 and 100 kilometres above Mars' surface.

The scientists say the formations look similar to mesospheric clouds on Earth, found about 80 kilometres above our planet's surface.

The researchers say that the Martian clouds are most likely made of carbon dioxide. They can only be viewed at night, as they are very faint and can just be seen reflecting sunlight against the darkness of the sky.

Using the SPICAM, the scientists observed sweeps of starlight - called profiles - as the light travelled through the Martian atmosphere.

After observing about 600 profiles in the atmosphere, the SPICAM showed that about one per cent of the stars dimmed noticeably when behind the 90 to 100-kilometre-high atmospheric layer.

The researchers concluded that miniscule dust grains 60 kilometres above the Martian atmosphere were likely where the carbon dioxide formed to make clouds, as vapour needs particles to form around in order to condense.

The dust grains were either originally chipped from rocks on the surface or debris from meteors, the scientists say.

The high-altitude clouds suggest the upper layers of Mars' atmosphere are denser than experts previously thought.

This would be a vital piece of information for mission planners who use the Martian atmosphere to "aerobrake", using friction in the outer atmosphere to slow down incoming spacecraft.

Photography: Solar Views

Source: Discovery Channel Reports, August 30 edition