An ancient rock in the Sultanate of Oman is the backdrop for a new study with consequences of the search for life elsewhere.
A report based on the study ‘Energetically Informed Niche Models of Hydrogenotrophs Detected in Sediments of Serpentinised Fluids of the Samail Ophiolite of Oman” suggests that water reacts with this rock to produce hydrogen, which could be an energy source for bacteria.
The report suggests that the study on Samail Ophiolite can help inform instrument and mission design and provide a valuable context in interpreting results from missions to Europa and elsewhere.
Ocean moons like Europa might be the best bet for finding life elsewhere. That’s why Nasa is developing the Europa Clipper mission and the European Space Agency (ESA) is developing the Jupiter Icy Moons Explorer mission.
But detecting life in Europa’s ocean — or the conditions for life — requires specific methods and instruments because the ocean is buried under kilometres of ice.
The Samail Ophiolite is a well-known geological feature in the Arabian Peninsula. It’s the largest and best-preserved ophiolite in the world, and it formed during Earth’s Late Cretaceous Period, which spanned from about 65 to 100 million years ago.
It’s commercially valuable because of its copper ore, but it’s also scientifically valuable for what it tells scientists about Earth’s geological history.
The Samail Ophiolite is important in the research because of the portion of the upper mantle rock it contains, says the report published in the ‘Universe Today’.
“When the rock from the upper mantle is reduced, which means there’s a lack of oxygen in the rock. There are more ionic sites in the rock that could react with oxygen if it were available”, it says.
For example, there’s more ferrous iron than ferric iron because there’s not enough oxygen to bond with all of the iron. This results in a mass of rock basically “waiting” for oxygen to fill all of its iconic sites. “This is what’s happening with the Samail Ophiolite. It reacts with water in a process called serpentinisation”, the study argues.
ENERGY SOURCE
The serpentinisation produces H2, which is molecular hydrogen. The H2 is food for microbes called hydrogenotrophs, which can metabolise it using oxygen and use it as an energy source.
An ophiolite is a section of the Earth’s oceanic crust and a piece of the underlying upper mantle. It’s an ophiolite when it’s lifted above sea level and exposed. Ophiolites often become embedded in the continental crust.
“It is believed that processes like serpentinisation may exist throughout the universe, and evidence has been found that it may occur on Jupiter’s moon Europa and Saturn’s moon Enceladus’’, lead author Alta Howells, now at Nasa’s Ames Research Center, said in a statement.
The results also touch on the energy needed for life and how that plays into our efforts on Europa. At the Samail Ophiolite, the methanogens living in the serpentinised fluids need more energy than methanogens found in fresh water and marine sediments.
Europa has a rocky core surrounded by an ocean, capped off with ice up to 30 km thick. Scientists know that there’s oxygen on Europa’s surface, though not much of it. It comes from charged particles in Jupiter’s atmosphere that irradiate the icy moon’s surface.
SOURCE OF LIFE
If oxygen makes its way through the ice somehow and into the ocean, it could contact the rocky core. But the rock has to be reduced to react with the oxygen to produce hydrogen as an energy source for life.
“As the Samail Ophiolite shows us, only rock low in oxygen, or reduced, can serpentinise to produce hydrogen. On Europa, radiogenic decay of the rock might expose reduced rock to oxygen. If the rock expands thermally, then microfractures might provide an opportunity for the oxygen in the water to contact the reduced rock”, the statement said.
Nasa’s Europa Clipper is scheduled to launch in October 2024. But it’ll take until April 2030 to arrive at Jupiter and enter into an orbit. A separate lander mission might launch in 2025 if approved, so by around 2031, data could be gathered from the icy ocean moon’s surface.
ESA’s Jupiter Icy Moons Explorer (JUICE) is scheduled for launch in 2023 and should arrive at Jupiter in 2031.
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