Composite images captured by an orbiting Nasa spacecraft have offered hints that fresh ice is forming in several areas on Saturn’s mysterious moon Enceladus.
With geyser-like plumes of ice erupting from the surface of the moon, scientists have suggested that life could lurk in its subsurface ocean.
The data shows that fresh ice is forming not just near the plumes, but in other areas of the moon, which looks like a reflective, bright white snowball to the naked eye.
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Gabriel Tobie, VIMS scientist with the University of Nantes in France, said: “The infrared shows us that the surface of the south pole is young, which is not a surprise because we knew about the jets that blast icy material there.
“Now, thanks to these infrared eyes, you can go back in time and say that one large region in the northern hemisphere appears also young and was probably active not that long ago, in geologic timelines.”
Enceladus’s ocean is likely heated and churned by hydrothermal vents like those on Earth’s ocean floors.
Some theories have suggested that such environments were where life first arose on Earth.
The researchers said that the same infrared features seen near the plumes also appear in the northern hemisphere.
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That tells scientists not only that the northern area is covered with fresh ice but that the same kind of geologic activity – a resurfacing of the landscape – has occurred in both hemispheres.
The resurfacing in the north may be due either to icy jets or to a more gradual movement of ice through fractures in the crust, from the subsurface ocean to the surface.
Managed by Nasa’s Jet Propulsion Laboratory in southern California, Cassini was an orbiter that observed Saturn for more than 13 years before exhausting its fuel supply.
The mission plunged it into the planet's atmosphere in September 2017.
While it still orbited Saturn, Cassini sampled a plume of material erupting from Enceladus’s surface, and analysis of the material suggested an environment where life could flourish inside the moon.
Researchers led by Lucas Fifer, of the University of Washington, found that the plumes are chemically different from the ocean beneath – changed by their 800 mph eruption into space.
It means that the surface of the moon could be much more hospitable to life than previously believed.
Fifer said: “Those high levels of carbon dioxide also imply a lower and more Earth-like pH level in the ocean of Enceladus than previous studies have shown. This bodes well for possible life.
“Although there are exceptions, most life on Earth functions best living in or consuming water with near-neutral pH, so similar conditions on Enceladus could be encouraging.”