September 6, 2012
Scientists Put Dates On Mars Climate Change For First Time
Lee Rannals for redOrbit.com — Your Universe Online
Researchers from the Niels Bohr Institute have dated climate history for Mars for the first time.The ice caps on Mars' poles are miles thick, composed of ice and dust and contain layers that can be seen in cliffs and valley slopes.
The layers are believed to reflect past climate on Mars, in the same way that Earth's climate history can be seen from the ice caps on Greenland and Antarctica.
The scientists were able to relate the layers in the ice cap on Mars' north pole to variations in solar insolation on Mars.
Solar insolation on Mars has varied dramatically over time, due to large variations in the tilt of Mars' rotational axis, and this led to dramatic climate various on Mars.
For years, people have been trying to link the solar insolation and layer formation by looking for signs of periodic sequences in the visible layers. These signals might be traceable back to known variations in the solar insolation on Mars, but so far scientists haven't determined where one could find a correlation between variations in insolation and the layers.
“Here we have gone in a completely different direction. We have developed a model for how the layers are built up based on fundamental physical processes and it demonstrates a correlation between ice and dust accumulation and solar insolation," Christine Hvidberg, a researcher in ice physics at the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen, said in a statement.
She said layer formation is driven by insolation and the dust rich layers can be formed by two processes: the first being increased evaporation of ice during the summer at high obliquity; and the second being the variations in dust accumulation as a result of variations in the axial tilt.
The model is simple, but physically possible and can be used to examine the relationship between climate variability and layer formation.
The scientists established a framework for the model that could explain the layer formation so that it was consistent with the observations.
Comparing the layer distribution in the model with measurements of the layer structure from high resolution satellite images of the ice, the team was able to find that the model is producing the complex sequence in the layers.
“The model dates the upper 500 meters of the northern ice cap on Mars, equivalent to approximately 1 million years and an average accumulation rate of ice and dust of 0.55 mm per year. It links the individual layers to the maxima in solar insolation and thereby establishes a dated climate history of the north pole of Mars over 1 million years,” Hvidberg said in the statement.
Although the model is based on a comparison with the visible layers in the upper part, preliminary studies indicate that the entire thickness and internal structure of the ice cap can be explained by the model and can explain how ice and dust accumulate on Mars' north pole.