Planetary science: Winds of change
Variations in the radiation reflected from the surface of Mars are contributing to climate change on the planet, by causing increased dust transport and wind circulation. A study predicts that the planet has warmed by around 0.65 degrees Celsius from the 1970s to the 1990s, which may in part have caused the recent retreat of the southern polar ice cap.
The fraction of solar radiation reflected from an object is called its albedo — and on Mars, large areas on the surface show a contrast in brightness or darkness with the areas next to them, resulting in albedo patterns, which can change in appearance over time. These changes in brightness have been generally attributed to the presence of dust, but until now their effect on wind circulation and climate has not been clear.
Lori K. Fenton and colleagues present predictions from a Mars global circulation model which show that these changes are having a much larger than expected effect on climate. Large swaths of the surface have darkened over the past three decades as they were swept free of dust, leading to elevated air temperatures and increased wind stresses. This creates a positive feedback loop between dust erosion and albedo. The authors conclude that albedo variations interact with, and can in part drive, other climate-influencing processes on Mars, and should be considered as an important component in future atmospheric and climate studies of the planet.
CONTACT
Lori K. Fenton (Carl Sagan Center, NASA Ames Reserach Centre, Moffett Field, CA, USA)
Tel: +1 510 786 7199; E-mail: lfenton@carlsagancenter.org or fenton@mintz.arc.nasa.gov