An ancient meteor site in Germany is being studied to help scientists develop a better understanding of how past life could have existed on Mars.
An international research team analysed samples from Nordlinger Ries, a 15-mile-wide impact crater in southern Germany.
The site’s geology and chemistry bear similarities to the Martian surface – in particular the Jezero crater north of the Martian equator.
Both Jezero and Nordlinger Ries featured liquid water in their distant past, making their chemical compositions comparable.
The Ries crater – in which a whole city was built more than 1,000 years ago – has layers of rock and minerals better preserved than almost anywhere on Earth.
Specifically, nitrogen isotopes in rock samples from the Ries crater are estimating the pH of ancient waters on Mars.
A sample of suevite rock formed nearly 15 million years ago by the Ries Crater meteorite impact. Similarly impact-generated rocks exist on the rims of ancient crater lakes on Mars
The Mars 2020 rover will land in a similarly structured and well-preserved ancient crater on Mars next year, called the Jezero crater.
Comparisons between the two will help scientists gain an understanding of how Mars once hosted oceans and life billions of years ago.
WHAT IS THE NÖRDLINGEN RIES CRATER?
Nördlingen Ries is an impact crater that formed on Earth about 14.8 million years ago from an asteroid that smashed into the surface of the Earth.
The crater, which is 15 miles in diameter, is most commonly referred to simply as Ries crater or the Ries.
The town of Nördlingen was built inside the crater in the 9th century at the very latest.
The Ries is recognised as an analog for Martian craters.
Ries was a rampart crater, which are almost exclusively found on Mars.
Rampart craters exhibit a ‘fluidized ejecta’ flow after impact of the meteorite.
‘The question that drives our interests isn’t whether there’s life on present-day Mars,’ said Professor Timothy Lyons at the Department of Earth Sciences at the University of California, Riverside.
‘We are driven instead by asking whether there was life on Mars billions of years ago, which seems significantly more likely.’
Mars is currently too cold – minus 81 degrees Fahrenheit – to support life as we know it.
NASA research already shows that Mars had a liquid water ocean around 4 billion years ago, but how that was possible is not completely certain.
Mars is further from the Sun than Earth is, and billions of years ago the Sun generated less heat than it does today.
‘To have made the planet warm enough for liquid surface water, its atmosphere would likely have needed an immense amount of greenhouse gas, carbon dioxide specifically,’ said Chris Tino, co-author of the study, which has been published in Science Advances.
It’s unlikely that ancient Mars had enough oxygen to have been home to complex life forms such as humans and animals, although microorganisms may have survived in alkaline lakes.
High-pH alkaline lakes are among the most productive ecosystems on Earth and are prime targets in the search for life on Mars.
Alkaline lakes also suggest sufficient carbon dioxide in the atmosphere to warm the planet and make liquid water possible.
The town of Nördlingen in Bavaria, Germany, which was built inside an impact crater known as Nordlinger Ries more than 1,100 years ago. The crater itself was formed by a meteorite around 15 million years ago
The team believe that Nordlinger Ries – which was formed around 15 million years ago after being struck by a meteorite – could help fill in the gaps regarding Mars’ history.
The German crater helps astrobiologists understand the alkalinity, pH and nitrogen content of ancient waters on Mars, which in turn suggests carbon dioxide composition, suggestive of life.
‘Ries crater rock samples have ratios of nitrogen isotopes that can best be explained by high pH,’ said co-author Eva Stüeken at the School of Earth & Environmental Sciences at the University of St. Andrews.
‘What’s more, the minerals in the ancient sediments tell us that alkalinity was also very high.’
Past Martian rock samples with mineral indicators for high alkalinity and nitrogen isotope data pointing to relatively low pH would demand extremely high levels of carbon dioxide in the past atmosphere.
The resulting carbon dioxide estimates could help solve the mystery of how an ancient Mars located so far from a faint early sun could have been warm enough for surface oceans and perhaps life.
Jezero Crater, the landing site for the upcoming Mars 2020 rover mission, which will touch down in February 2021 to seek signs of habitable conditions on Mars in the ancient past
When samples from NASA’s Mars 2020 rover mission are brought back to Earth, they could be analysed for their nitrogen isotope ratios.
This data could confirm the team’s suspicion that very high levels of carbon dioxide made liquid water possible and maybe even some forms of microbial life long ago.
‘It could be 10-20 years before samples are brought back to Earth,’ Professor Lyons said.
‘But I am delighted to know that we have perhaps helped to define one of the first questions to ask once these samples are distributed to labs in the US and throughout the world.’
WHAT DO WE KNOW ABOUT NASA’S MARS 2020 ROVER?
Nasa’s Mars 2020 rover will search for signs of ancient life on Mars in a bid to help scientists better understand how life evolved on our own planet.
The machine will explore an ancient river delta within the Jezero Crater, which was once filled with a 1,600-foot (500-meter) deep lake.
It is believed that the region hosted microbial life some 3.5 to 3.9 billion years ago.
Nasa’s Mars 2020 rover (artist’s impression) will search for signs of ancient life on Mars in a bid to help scientists better understand how life evolved on our own planet
The $2.5 billion (£1.95 billion) Mars 2020 is planned to launch in July 2020, and land in February 2021.
Mars 2020 is designed to land inside the crater and collect samples that will eventually be returned to Earth for further analysis.
Nasa says a second mission will need to fly to the planet and return the samples, perhaps by the later 2020s.
This concept art shows the Mars 2020 rover landing on the red planet via NASA’s ‘sky-crane’ system