Clue to ancient life on Mars found inside meteorite: 'Wild buffet of early Martian history'
Thermal activity nurtured early life on Earth, now similar conditions have been found to have occurred on Mars 4.45 billion years ago.
Inside an ancient meteorite that collided with Earth, scientists have uncovered evidence of what could be the oldest hot water activity on Mars. Similar hydrothermal vents were a key component in creating conditions for early life on Earth, so finding evidence of them on the Red Planet 4.45 billion years ago helps pinpoint when Martian life could have existed.
Study co-author Dr Aaron Cavosie from Curtin’s School of Earth and Planetary Science explained to Yahoo News that it’s hard to search directly for life on Mars. So they look for chemical signs in rocks that suggest habitats that could have nurtured it instead.
“Hot water is a pretty useful thing if you're trying to wrap your head around whether Mars could have been habitable. So finding finding evidence of it is a big deal,” he said.
Related: Path of ancient coastline found on surface of Mars
Why meteorites are key to understand ancient Mars
To look for water on Mars before 4.1 billion years ago, during the pre-Noachian period, scientists can’t look at the planet itself. That’s because the surface has been severely denuded, and orbiters and rovers can’t yet identify which rocks are from the period.
Ancient meteorites that have made their way to Earth are a more reliable source of evidence. Signs of water had been previously documented inside the famous Black Beauty meteorite, but what’s different about the recent study is the temperature of the liquid and its age.
How was the Mars meteorite formed?
The Black Beauty meteorite, also known as (NWA) 7034, was created out of rock fragments and minerals that accumulated over time on the surface of Mars and eventually became a rock.
“Black Beauty is a wild buffet of the early Martian history. It has a lot of different pieces in it that all have their own stories,” Cavosie said.
“The grains we studied in the meteorite were about half the width of a human hair. And while it's very small, it’s also very interesting.”
How did scientists find evidence of water in the meteorite?
Curtin University has been studying Black Beauty for years. The recent analysis was able to establish the presence of hot water by using nano-scale imaging and spectroscopy to examine the grain of tiny zircon crystals in the meteorite.
Zircons are also found across the Earth, and they’ve been used to locate the earliest signs of freshwater on the planet. Separate research from July found evidence in crystals that rainwater was falling on Australia 4 billion years ago, around 500 million years earlier than previously thought.
Zircon is predominantly made of just three elements – oxygen, silicon and zirconium. And some elements at very low abundance levels often sneak into the crystals when they are forming, like uranium.
“But we found elements you don’t normally find in zircon such as iron, aluminium and sodium. And these were surprising to us,” Cavosie said.
What was special about the zircon crystals in the meteorite?
Normally those elements are associated with zircons damaged by the uranium they contain. The fractures in the rock allow fluids that could not normally get inside the crystal to work their way in, bringing in other elements.
“But that wasn’t the story here," Cavosie said. "In this case, they were all highly organised into nice discrete layers just like those inside a growing onion.”
The strange composition of the zircon prompted the team to investigate what could cause it to form in such a “beautiful” organised way. The team turned their attention to rocks on Earth and found a similar example at South Australia’s Olympic Dam mine.
It's recognised that the creation of ore deposits inside the mine were aided by hydrothermal processes as well.
“A study done previously found the same type of patterns for elements like iron and aluminium that we found in the Martian zircon,” Cavosie said.
“These are signatures of zircon grown in a hydrothermal environment where water assists in the mobility and the delivery, and the incorporation of these elements into the growing zircon.”
The lead author was Dr Jack Gillespie from the University of Lausanne, who was a Postdoctoral Research Associate at Curtin’s School of Earth and Planetary Sciences. The research has been published in the journal Science Advances.
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