Wednesday, March 28, 2012

A glow in the Martian night throws light on atmospheric circulation

A faint, infrared glow above the winter poles of Mars is giving new insights into seasonal changes in the planet's atmospheric circulation. The tell-tale night emission was first detected in 2004 in observations made by the OMEGA imaging spectrometer on ESA's Mars Express orbiter.

Writing in a recent issue of the Journal of Geophysical Research, a team of French scientists reported on the first detection of an infrared emission above the polar regions of Mars. The emission, at a wavelength of 1.27 microns, was detected on three occasions (in 2004, 2005 and 2006) during a series of 40 observations made by OMEGA above the planet's limb.

Infrared emissions are not unusual in planetary atmospheres. In the upper atmospheres of both Venus and Mars, carbon dioxide (CO2) and nitrogen (N2) molecules are split or photodissociated by solar ultraviolet (UV) light. This produces oxygen and nitrogen atoms in the region known as the thermosphere, at an altitude of about 80-90 km above each planet's dayside. Read More