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22 Mar

Come my friend

‘Tis not too late to seek a newer world-

Alfred, Lord Tennyson”

Mars is on the mind of scientists for the reason addressed by Lord Tennyson. There is noticeable differences between Earth and Mars. The Earth’s crust is formed by tectonic plates that move slowly, driven by convection currents in the molten core. But on Mars there are no tectonic plates. The surface of Mars is shaped by volcanoes, cratering and vast magma upheavals similar to the ones that created The Tharsis bulge and the Valley Marinensis (Fig.1). Mars has the largest volcano in the Solar system: Olympus Mons, covering na área 600 km in diameter and 27 km high.


The Tharsis region. Image credit: Wikipedia.

A martian day is only 3 % longer than Earth’s day, while the year is equivalent to 687 Earth’s day. Due to its eccentricity (the most one after Pluto), see Fig.2, the solar input varies significantly during the martian year.

Mars eccentricity is higher than Earth. Image credit:

Mars eccentricity is higher than Earth. Image credit:

There is water in vapour form in the atmosphere and in the ice caps at poles; evidence exists that water in liquid form was present before on Mars. Probably due to Mars eccentricity the southern hemisphere has very little water vapor (0 to 0.3 precipitable micrometer, but in contrast the northern hemisphere shows a significant amount of water (up to 75 micrometers at 70-80 ^o N). On the basis of the abundance of water vapor in the polar region, an estimate of the lower limit on the atmospheric temperature can be given, being about 205 K (or -68 ^oC). This is an indication that the permanente polar cap is made of water ice (confirmed by Viking spacecraft) with a tickness between 1 meter and 1 kilometer. The atmosphere contains concentrations of nitrogen, árgon, carbon dioxide, molecular oxygen, atomic oxygen, and nitric oxide that are detectable. However, the thiness of the Martian atmosphere was disappointing, with a value one-tenth of Earth’s. According to Anders and Owen, five processes working in combination may have been responsible for the thin atmosphere: i) a small endowment of volatiles gases; ii) incomplete outgassing from the interior; iii) recondensation or trapping in surfasse regions; iv) catostrophic loss of the early atmosphere; v) gradual escape of the lighter constituents.

Olympus mons on Mars. Image credit: http://annesastronomynews

Olympus mons on Mars. Image credit: http://annesastronomynews

But this situation results, too, because Mars has only half Earth’s diameter, 11% its mass and 38% its gravity, increasing the probability of gas escape at the upper layers of the original atmosphere.

The gravity on Mars is lower than on Earth; a person weighing 100 kg on our planet would have 38 kg on the surface of Mars…

See this wonderful movie prepared by NASA showing the intricacies of a mission to the Red Planet. Astounding!

[1] – Expedition Mars, by Martin J.L. Turner

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