What we’ve learned about the red planet from 260+ Martian meteorites
A bubble of Martian atmosphere
Small planets cool quickly and it has long been suspected that Mars’s core has largely but not totallycrystallized. This means Mars has mostly lost the protective magnetic field that deflects cosmic radiation.
But we are confident Mars once had an ocean, containing water as we know it. The temperature was above freezing and conditions were suitable for life. The stripping away of the magnetic field early in Mars’s history means this ocean is long gone and the average temperature is now -65℃, but frosts, clouds and ice caps remain.
Not being fortunate enough to roam the deserts of Africa or the icy plateaus of Antarctica, I instead found my first Martian meteorite sitting in a cabinet in a gem store in the small New Zealand town of Akaroa.
Using a scanning electron microscope, my examination revealed it was a shergottite, one of themost common Martian meteorites— equivalent to what we know on Earth as basalt. If it’s basalt, though, how do we know it’s from Mars?
Read more:How to spot Mars: See the red planet in the sky the day Nasa’s Perseverance rover lands
There are several ways of recognizing a Martian meteorite. One is from its gas content. When a meteorite strikes the surface of Mars, the “target” rocks are subject to such great pressures they partly melt and trap Martian atmosphere within gas bubbles. Some of these rocks are then ejected from the planet — becoming meteorites themselves.
The gases in these meteorites can be measured back on Earth and compared to the known Martian atmosphere, which comprises95% carbon dioxideand distinctnoble gasconcentrations.
The thousands of craters scarring Mars’s surface mean it is ancient. This was confirmed when one meteorite was dated to be4.4 billion years old. Properties of some other Martian meteorites show Marsformed within 13 million yearsof the formation of the Solar System. This in turn means some of the first planetary crust that formed on Mars likely still exists at the surface.
Old and cold — but not dead
This inference, along with some meteorite mineral and isotopic properties, implies Mars has not been shaped by plate tectonics — the global process that formed the continents, mountain ranges and ocean basins on Earth.
And, as most dated Martian meteorites are less than 1.5 billion years old, volcanism has continued throughout its history. Mars may be cold but it is not dead.
Martian meteorites also hold clues about how people may one day be able to survive on the planet.
While living in hollowed out lava tubes in Martian basalt may appeal to some hopeful interplanetary settlers, we’ll ultimately need to build shelters to protect us from the cosmic radiation and vast dust storms that engulf the planet.
Martian meteorites show olivine, a magnesium-silicate mineral, is common. Experiments are underway to assess the use of a breakdown component, magnesium carbonate, to form a concrete binder from which we could fashion buildings.
Martian meteorites show that big insights can be gleaned from little rocks and reveal what Mars is made of.
This article byJames Scott, Associate Professor in Geology,University of Otago, is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
An independent news and commentary website produced by academics and journalists.An independent news and commentary website produced by academics and journalists.
Get the TNW newsletter
Get the most important tech news in your inbox each week.
