MODELING MARTIAN SNOWS

Hartmann, a senior scientist at the nonprofit Planetary Science Institute in Tucson, Arizona, said he and his team confirmed the earthly computer models’ effectiveness by using them to forecast conditions on Mars.

New satellite observations of glaciers, ice flows and other features on the red planet showed that the models’ predictions corresponded with what was on the Martian surface, Hartmann said in a telephone interview.

One key difference between Earth and Mars is their tilt, he said. Earth’s axis is fixed, with very small variations, at 23.5 degrees, held steady by the gravitational pull of our moon. This tilt is responsible for changing seasons as Earth moves through the year, alternately tipping its northern and southern hemispheres toward the sun.

Mars lacks a big moon to stabilize its tilt, and its rotational axis can vary as much as 70 degrees toward the sun. When that happens, polar ice evaporates and puts moisture into the Martian atmosphere, which dumps snow, ice and ultimately glaciers in Mars’ mid-latitudes. The last time this happened, astronomers say, was between 5 million and 20 million years ago.

Factoring in the planet’s varying tilt, topography, atmosphere and other information, the climate models forecast specific regions for massive snowfalls, and the remnants of those snowfalls are right there, Hartmann said. So are ice flows and other features, viewed by NASA’s Mars Reconnaissance Orbiter.

“We do have a lot of public figures, in our country particularly, saying that the global climate modeling studies have very little value,” Hartmann said. “If the global climate modeling people can run these models on Mars and we actually see things that come out of the model on another planet, then the climate modeling people must be doing something right.”