Sea sponges and other colourful marine creatures could be living beneath the surface of Mars, according to new research.
Salty subterranean lakes on the Red Planet are capable of producing enough oxygen to support microbes – and even simple animals, say scientists.
Life on Earth began when algae evolved photosynthesis – the process of turning sunlight into energy – and started exhaling oxygen as waste. This sent atmospheric levels soaring.
But on the surface of Mars only trace amounts occur from the light-induced breakdown of carbon dioxide – leading experts to rule out the possibility of life.
However, a computer model now shows this does not apply to the briny underground lakes on the Red Planet composed of salt and water.
And the US team found the oxygen concentrations are highest in the polar regions.
Scientists have been searching for life on Mars since the dawn of the space age and excitement is growing they are getting close.
The latest study published in Nature Geoscience follows the recent discovery of a 12 mile wide lake at the southern ice cap.
That created a worldwide furore and this will only add to it.
Cold water contains more oxygen than warm because the molecules are more tightly packed, making it harder for them to escape.
Corresponding author Dr Vlada Stamenkovic said the briny water will also be abundant in calcium and magnesium which which boost bone and metabolism, respectively.
He said places “with sufficient oxygen available for aerobic microbes to breathe” may be all over the Red Planet.
He added: “Moreover, about 6.5 percent of the total Martian surface area could support far higher dissolved oxygen concentrations, enabling aerobic oases sufficient to sustain the respiration demands of more complex multicellular organisms such as sponges.”
Dr Stamenkovic, a planetary scientist at the California Institute of Technology in Pasadena, said such environments are common near the Martian poles.
The humble sea sponge comes in a variety of beautiful shapes and colours and is the most primitive of all multi cellular animals.
Its arrival on Earth around 640 million years ago kick started life.
There are up to 10,000 different species and significantly, most live in salt-water. They can be found stuck to the floors of oceans and rivers.
They feed by filtering water and can even reproduce sexually through males releasing sperm that is carried by the current and picked up by females.
The researchers calculated how much oxygen could be dissolved in the Martian lakes under the various pressure and temperature conditions expected just below the fine soil, or regolith.
Dr Stamenkovic said: “Due to the scarcity of oxygen in the modern Martian atmosphere, Mars has been assumed to be incapable of producing environments with sufficiently large concentrations to support aerobic respiration.
“Here, we present a thermodynamic framework for the solubility of oxygen in brines under Martian near-surface conditions.”
Simulations showed there may be underground lakes today with enough dissolved oxygen to support life “across the planet” – with the likeliest locations at the polar regions.
Lower temperatures at higher latitudes boosts the oxygen content of salty water, he explained.
Dr Stamenkovic said: “Even at the limits of the uncertainties, our findings suggest there can be near surface environments on Mars with sufficient oxygen available for aerobic microbes to breathe.”
Dissolved salts of magnesium, calcium and sodium keep liquid fluid – even below freezing point.
They are known to be present in Martian rocks and are believed to maintain the briny miniature sea at the South Pole.
This is because they reduce the melting point of water to minus 74C.
Dr Stamenkovic said little attention has been given to the role of oxygen on Mars, due to its scarcity.
But geochemical evidence from Martian meteorites suggest it once had large amounts thanks to its warm atmosphere and liquid oceans which played a role in the weathering of its crust.
Dr Stamenkovic said: “Aqueous environments, in the form of brines, can exist today at, and especially below, the surface despite the thin atmosphere and overall cold climate.”
Recent evidence demonstrates hydrated magnesium and calcium salts at various locations on the surface and shallow subsurface.
This suggests there could be oxygen “comparable to the concentrations in Earth’s oceans today.”
Dr Stamenkovic said: “Thus, in principle, Mars could offer a wide range of near-surface environments with enough dissolved oxygen for aerobic respiration like that seen in diverse groups of terrestrial microorganisms.”
The findings also have implications for the search for life on other planets and moons.
On Earth, aerobic respiration followed the emergence of photosynthesis. But by sourcing oxygen in a different way, Mars shows us this need not be the case.
Added Dr Stamenkovic: “Our findings may help to explain the formation of highly oxidized phases in Martian rocks observed with Mars rovers, and imply opportunities for aerobic life may exist on modern Mars and on other planetary bodies with sources of oxygen independent of photosynthesis.”
In July an Italian team stunned the world when they announced the discovery of a vast Martian lake deep beneath the South Pole under a 1.5 km thick layer of ice.
The water appears to be composed of magnesium, calcium and sodium perchlorate, which together act like an anti freeze that maintains its liquidity.
The thought there could be Earth like creatures there right now will only add to the excitement.
Dr Stamenkovic said: “Our study focused on near-surface environments. Recent results have indicated the potential existence of calcium and magnesium perchlorate rich brines at a depth of 1.5km.
“Our results imply the oxygen solubility in such a reservoir would be high, raising the possibility they could be rich in oxygen if the supply either from intermittent communication with the atmosphere or from the radiolysis of water is sufficiently large.”
There are some insects, fish and other organisms on Earth that are capable of life at subzero temperatures. Mars lacks the food webs needed to sustain higher organisms – but many microbes are capable of inhabiting hostile environments even when no other organisms are present.
We know from research on Earth they can survive in brine.