Mars: 40 ice ages in the last 5 million years

The sharp fluctuations in the angle of inclination of Mars compared to the Sun caused the accumulation of underground ice also in middle latitudes and not only at the poles

Fluctuations in Mars' self-rotation have brought Mars to 40 ice ages in the past 5 million years and allowed thick layers of ice to survive away from the poles, an astronomer says.

Several spacecraft have revealed details about the ice ages on Mars. About 4-5 million years ago, precipitation events occurred that released amounts of snow and ice that accumulated around the poles. Today, the only place you can see ice on Mars is in the ice caps at the planet's poles, but in recent years, spacecraft orbiting Mars have found solid evidence that vast areas of subsurface ice lie closer to the equator, in areas scientists call mid-latitudes.

How much ice ended its way away from the poles - this still remains a mystery. The answer to this may be found in the fluctuations of the orbit of Mars, concludes Norbard Schughofer of the Institute of Astrobiology at the University of Hawaii.

The mechanics of the moon

Earth's axis of rotation is tilted by 23.5 degrees, a fairly constant rate thanks to the gravitational influence of our moon. Mainly because Mars lacks the stabilizing Moon, its oscillations can vary by 10 degrees from the current inclination of 25 degrees.

The researcher, who used computer simulations that although not wild, these fluctuations change the amount of sunlight reaching the surface of Mars and can cause huge amounts of ice to move between the poles and the rest of the planet every 120 thousand years.

And this is how it works: when the axis of rotation of the planet moves in one direction, the sun's rays disappear from some areas and radiate more strongly in other areas. The areas exposed to sunlight become drier and warmer and this causes the ice to disappear completely, except for the high latitudes. The evaporated ice provides water vapor to form new ice when the sun returns and the humidity rises. In the humid climate, the researcher says, the water vapor seeps into the Martian soil, freezes and forms pore ice, which consists mainly of soil with ice droplets filling the pores.

These fluctuations leave two types of ice on or near the surface of Mars: an ancient, massive ice surface, and the fresh pore ice, less than half a million years old. Dry land covers both of these types of ice.

"Today, this phenomenon enables the existence of porous ice in the middle latitudes and a three-layer stratification in the high latitudes," says Shughofer in an article he published on September 13 in the journal Nature. In the high latitudes, the original ice surfaces are covered with a thin layer of porous ice, and above this a surface of dry sediments.

When the Phoenix spacecraft lands on Mars, during 2008, near the North Pole, Shughofer expects that it will "see" these ice layers.