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Welcome to Mars! Whilst the martian environment is considered ‘most similar to Earth’s’ when compared to other planets in our Solar System, that’s a bit like saying an insect is ‘most similar to a human’ when compared to a rock, a spoon and cellphone. Whilst both of the above might be true, it really doesn’t to justice to the weird and wonderful nature of the martian environment. Both Mars and Earth are ‘terrestrial’ planets, so called because you’re able to wander around on them, like the Apollo astronauts did on the lunar surface 30 years ago. You would feel a little lighter on Mars than you’re used to here on Earth though – because it’s much smaller than the Earth: about half as wide and only about 1/8th of the Earth’s mass.

Mars as seen by the Hubble space telescope

The red planet’s characteristic hue comes from huge amounts of rusty (iron oxide) dust strewn across its surface, which is mostly composed of silicate rocks and other metals. However the dry, dusty Mars that our minds conjure pictures of when we imagine it, is a relatively new phase in Mars’ life (compared to its current age of around 4 and a half billion years). We believe, because of strange, wavelike patters on the Martian surface, that is was once much hotter and wetter than it is now. Currently, Mars’ surface temperatures sit between about -90 and -10 degrees Celsius, far too cold for anything to be ‘wet’ as any water would instantly freeze at those temperatures. This begs the obvious question: What happened to Mars that so drastically changed its atmosphere? (and importantly, could the same thing happen to Earth?)

Image Credit: NASA

A martian sunset captured by the Mars Exploration Rover Spirit (Image Credit: NASA/JPL/Texas A&M/Cornell)

The answer to this lies deep within the Mars core, where Mars once again reminds us of just how different it is from our home here on Earth. Mars has much weaker magnetic field than the Earth’s, in fact the only field it has comes from magnetic elements in the dust that covers it’s surface. Compare that to Earth which has a strong magnetic field due to the presence and movement of iron deep within our planet. Why is this important? Our magnetic field is what protects us from much of the violent debris that are constantly being fired out towards us by solar storms on the surface our Sun. Without this protection, this so called ‘Solar Wind’ slowly stripped Mars of much of its atmospheric gasses, leaving it cold and with a much thinner atmosphere than Earth (and thus lower atmospheric pressure). What’s left of the martian atmosphere is mostly made up of carbon dioxide, much of which freezes as ‘dry ice’ at Mars’ polar regions during its winters. All in all, when you look out at Mars tonight (it’s the bright orange-red object mid-way up in NZ’s northern skies during early currently), think fondly of our brave Kiwi-naughts huddled in their heated, pressurised space suits as they brave the wilds of Utah. And all in the name of science!

co-authored by Jared Lee and Elf Eldridge