New Mars Observations
The Omega instrument aboard ESA’s Mars Express, detected in the equatorial region of Mars, a high-altitude carbon-dioxide-ice (CO2) cloud. Elongated across the rim of an impact crater, the shadow of the cloud was spotted on the surface. Mars is usually cloud-free because of its thin atmosphere and scant moisture. Vast areas of Mars are covered by dust storms. On earth, day ice is known as frozen carbon dioxide.
Carbon dioxide, the main component of Mars’ air, freezes into clouds so dense they dim the sun by about 40%. “This is the first time that carbon dioxide ice clouds on Mars have been imaged and identified from above”, said Frank Montmessin of the Service d’Aeronomie, University of Versaillles and lead author of a paper in the Journal of Geophysical Research. “This is important because the images tell us not only about their shape, but also about their size and density. Up to this time, only indirect information suggested what the clouds consisted of.
The European Space Agency’s orbiting Mars Express made these new observations. The fact that the carbon-dioxide clouds were high, some 50 miles, and several hundred miles wide was unusual. According to Montmessin’s team, they’re thicker than expected. Another observation was that the clouds are made of particles that are larger than expected. The particles are more than a micron wide (one-thousandth of a millimeter). It was thought that particles of this size wouldn’t be expected to form in the upper atmosphere or to stay aloft for very long before falling back toward the surface.
The clouds “cast quite a dense shadow and this has a noticeable effect on the local ground temperature”, Montmessin said. “Temperatures in the shadow can be up to 10 degrees Celsius (50 degrees Fahrenheit) cooler than their surroundings, and this in turn modifies the local weather, particularly the winds.”
Researches think that because of extreme variations in daily temperature that occur close to the equators, these clouds are found there. “The cold temperatures at night and relatively high day-time temperatures cause large diurnal waves in the atmosphere”, Montmessin explained. “This means there is a potential for large-scale convection, particularly as the morning sun warms the ground.”
At the root of the earth’s weather is convection-warm air rising. Researchers explain that bubbles of warm gas rise on mars and at altitude the carbon dioxide condenses. This releases heat, causing the gas and ice particles to rise higher. Water vapor condenses around tiny particles, often dust or salt, to form clouds on earth. It is not known what the Martian moisture is condensing around. According to researches, it could be dust, micrometeorites, or tiny crystals of water ice.
This entry was posted on Wednesday, January 16th, 2008 at 12:37 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
