Mars may have been more Earth-like than thought

• Compounds in Martian rocks hint at high levels of oxygen, liquid water
• Vegetables grown in Red Planet’s soil found to be safe to eat

Earth’s red neighbour may once have been more like our home planet than we thought.

Chemical compounds found in Martian rocks suggest the planet’s atmosphere contained higher levels of life-sustaining oxygen, as well as pools of liquid water.

The discovery published in the journal Geophysical Review Letters was made by United States National Aeronautic Agency (NASA’s) Curiosity Rover, which, has been periodically chewing up Martian rocks and tasting the chemicals to build up a picture of the planet’s history.

NASA’s Curiosity rover found manganese oxides in rocks on Mars.

Researchers say this suggests the planet’s atmosphere once contained higher levels of life-sustaining oxygen, as well as pools of liquid water.

In order for the compounds to form, they would have required an oxidising atmosphere – rich in oxygen.

But the team believes that rather than being caused by microbes – as on Earth – the atmospheric oxygen on ancient Mars was the result of water molecules being split by solar radiation.

While sampling at the Gale Crater, it turned up high levels of manganese, with more than a quarter tied up in the form of manganese oxide, which mission scientists say hints at an Earth-like past.

Also, researchers have shown that it is not only possible to grow vegetables in soil similar to that found on Mars, but they are also safe to eat.

Scientists at the Wageningen University in the Netherlands were able to achieve abundant harvests of ten different crops including radishes, peas, tomatoes, cress, rocket and rye.

A planetary scientist at Los Alamos National Laboratory in New Mexico, Dr. Nina Lanza, explained: “The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes.”

Here on Earth, these compounds are made from a mix of water and highly oxidising conditions, which requires lots of oxygen in the atmosphere.

According to the researchers, their presence in rocks today is a sign that ancient Mars once had oxygen in its atmosphere as well as pools of water on the surface.

“These high-manganese materials can’t form without lots of liquid water and strongly oxidizing conditions,” said Lanza.

“Here on Earth, we had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose due to photosynthesising microbes.”

But signs of oxygen in the ancient Martian atmosphere may not necessarily be the ‘smoking gun’ for life on Mars. The team believes geological processes could account for the presence of oxygen, rather than Martian microbes.

“One potential way that oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field,” added Lanza.

Data collected from satellites as well as rovers on the surface indicates the red planet likely had more water in its past, but billions of years ago its magnetic field began to fail.

Without this layer of protection, the Martian surface would have been bombarded with solar radiation, shearing the bonds between atoms and splitting water into hydrogen and oxygen.

In its thin atmosphere, the lighter hydrogen gas likely evaporated into space, while the heavier oxygen atoms hung around long enough to react with other atoms to form stable compounds – such as the manganese oxides found in the rocks and the red iron oxides of the rusty Martian soil.