Last updated June 29, 2018 at 3:25 pm
Crystals found in a meteorite from Mars show the planet formed extraordinarily quickly after the first beginnings of the Solar System.
The Valles Marineris hemisphere of Mars. Credit: NASA/JPL-Caltech
The Red Planet may have cooled to form a rocky surface just 20 million years after the formation of the Solar System itself, according to the latest research on zircon crystals from a Martian meteorite.
This incredibly rapid formation means that Mars could have had potentially habitable conditions a full 100 million years before Earth.
And this, say the researchers, rewrites the history of our solar system as it shows planets can form rocky surfaces ten times faster than previously believed possible. With crust surfaces required to form life as we know it, the finding raises the possibility that life could have formed on Mars with a big head start to that on Earth.
Backtracking through planetary history
The history of the early Solar System is challenging to explore as so few of the objects from that time have remained intact. This is especially true on the easiest place to access by our experiments, Earth, with many scars and artefacts being lost in a surface renewed and reshaped by tectonic activity, water, and life.
Therefore, any relics from that ancient time, nearly 5 billion years ago, have to be hardy and resistant to high temperatures, pressures and erosion.
The geologist’s preferred time capsule is a naturally occurring mineral called zircon that, when crystallised, is resistant to all but the most destructive events imaginable, including meteor strikes.
A region of Western Australia, known as Jack Hills, contain ancient zircons formed on the Earth as old as 4.37 billion years making this one of the most ancient preserved areas on our planet.
However, it’s not the Earth rocks that researchers in the Nature publication are interested in but rather something that landed on Earth. These are Martian meteors that have carried even older remains of the Red Planet to Earth, and again the surviving fragments of interest are zircon crystals.
The zircons extracted from Martian meteorite NWA 7034 Credit: Bouvier et al, Nature
While it may seem incredible that material, ejected from Mars in its own meteor strike, can travel all this way and land on Earth to be assayed by geologists, there are in fact over one hundred meteorites from Mars known to have impacted here.
The seven crystals found in crushed samples of Martian meteorite, NWA 7034, that landed in North West Africa and range in size from 50 to 110 micron (no wider than a human hair).
The crystals act as an impenetrable host for uranium to undergo radioactive decay into lead, similar to the more well known Carbon dating technique. With this uranium-lead dating the oldest zircon crystals are estimated to be 4,476.3 million years old with an uncertainty of less than a million years, making them at least 100 million years older than the zircons from Jack Hills.
The timeline of the Solar System
What makes this extraordinary is that the first solid material formed around the young Sun 4,567.3 million years ago.
This means these particular crystals had formed on the rocky surface of Mars in just 90 million years, when Earth was still an ocean of magma after the collision which formed the Moon.
For Mars to get to this stage where it was more hospitable to life than Earth 100 million years earlier, sets an even more stringent time on the rapidity of the formation of Mars itself.
Looking at the characteristics of other chemicals in the zircons, the researchers found that Mars likely had a primordial crust as soon as 20 million years after the beginnings of the Solar System.
This means in less than 10 million years after the formation of the Sun, orbiting gas and dust grains stuck together to growing into ever larger pieces that slammed together as planetesimals until finally an entire world had accreted.
This accretion was so violently that it melted the entire world until that was a single magma ocean. Within another 10 million years that magma ocean had cooled and solidified to form a solid surface.
This rapid rate of formation of 20 million years from nothing to a planet with a crust sets a new benchmark for planetary formation in our Solar System.
As a related Nature News & Views article makes clear, if the Solar System were a day old then Mars had fully formed within the first 6 minutes, and a thirty minute head start on Earth for the potential formation of life.
