A chemical camera sitting atop Curiosity, the Mars rover, has spotted signs that the Red Planet may have once had oxygen in its atmosphere, fuelling further speculation that it was once Earth-like.
Today, Mars is a barren wasteland. Its surface is dry and caked in rust-coloured iron oxide dust particles – a stark difference from the Earth, which is mostly covered in water.
Yet after missions to Mars began more than 40 years ago, scientists have slowly uncovered signs that it may have had been more similar to the Earth in its past than it is now. Scientists' most recent finding of manganese oxide – a metal rust that looks like soot – in Martian rocks indicates that the planet may once have had oxygen in its atmosphere.
The results were published in Geophysical Review Letters and pinpoint the manganese oxide to sandstones in the Kimberley region embedded inside the Gale crater.
The chemical camera (known as ChemCam) analyses rock and soil samples by using a laser to zap target materials. The beam excites electrons in the sample causing it to give off a glow, the colour of which depends on the types of atoms it contains. The light is analysed by a spectrometer in the ChemCam and identifies the types of atoms in the sample.
"The only ways on Earth that we know how to make these manganese materials involve atmospheric oxygen or microbes," said Nina Lanza, a planetary scientist at Los Alamos National Laboratory and lead author on the study.
"Now we're seeing manganese oxides on Mars and wondering how the heck these could have formed.
“Microbes seem far-fetched at this point, but the other alternative – that the Martian atmosphere contained more oxygen in the past than it does now – seems possible,” Lanza added.
The presence of manganese oxide on the Earth marks a point when oxygen levels began to rise, after photosynthesising microbes began releasing oxygen into the air.
Researchers believe that the high levels of oxygen may have floated into Mars’ atmosphere after water was whisked away as the planet lost its magnetic field. Having a magnetic field shields a planet from harmful solar winds which can blow away its atmosphere.
The theory is not too far-fetched as last year, NASA’s Mars Reconnaissance Orbiter detected signatures of hydrated minerals on the planet’s slopes. An imaging spectrometer also captured mysterious streaks that scientists believe were made by the flow of water carving grooves into the Red Planet's surface.
This is not the first detection of manganese oxide on Mars. Another team of researchers from Europe presented their results (PDF) at the European Geosciences Union General Assembly earlier this year. They found three per cent of Martian rocks contain manganese oxide. ®