Why do a group of scientists believe that life beyond earth may exist?

Around 20 years ago, a group of Stanford scientists noticed signs of what could mean life beyond Earth: a double ridge formation on the surface of Jupiter’s icy moon Europa, with the same gravity-scaled geometry landform in Northwest Greenland ice sheet.

It means, under the thick icy shell with a thickness between 20 to 30 km, there might be pockets of water that are  habitable – for possibly aliens, but more likely for less exciting creatures, microbes.

The new findings also means that if ever humans were to colonise a new planet, they could be looking at Europa instead of Elon Musk’s destination, Mars.

In a study published in Nature Communications this week to sum up their two-decade-long research, the scientists revealed that Europa might have twice as much water as Earth, where scientists believe life first emerged as marine microbes.

The scientists questioned if the double ridges on Europa formed in the same way it formed in Greenland, after fracture of ice around water that refreezes inside the ice sheet.

"In Greenland, this double ridge formed in a place where water from surface lakes and streams frequently drains into the near-surface and refreezes," said lead study author Riley Culberg, a doctoral student in electrical engineering at Stanford.

"One way that similar shallow water pockets could form on Europa might be through water from the subsurface ocean being forced up into the ice shell through fractures—and that would suggest there could be a reasonable amount of exchange happening inside of the ice shell."

If a similar mechanism accounts for Europa, the fourth-largest of Jupiter's 79 known moons, the water pockets are likely to help circulate chemicals necessary for life through the fractures in the ice shell.

And finding such a signature promising pocket of water like this is “very exciting”, Dustin Schroeder, an associate professor of geophysics at Stanford University told The Guardian.

However,  the Stanford scientists were not the first to spot the double ridges on Jupiter’s moon.  Data from NASA’s Galileo spacecraft in the 1990s suggested that a global ocean exists beneath the frozen ice surface of Europa. But the researchers were able to understand how they formed.

Then in 2015, a NASA mission, Operation IceBridge, collected surface elevation and radar data of the ice sheet in Greenland for two years, revealing how the double ridges were formed after refrozen  water inside ice sheets caused distinct peaks to rise. 

The breakthrough data raised hopes of striking similarity with Europa even more.

"The mechanism we put forward in this paper would have been almost too audacious and complicated to propose without seeing it happen in Greenland," said study senior author Dustin Schroeder, an associate professor of geophysics at Stanford University's School of Earth, Energy & Environmental Sciences. 

Culberg says this was the first time that scientists were able to watch something similar happen on Earth and actually observe the subsurface processes that led to the formation of the ridges.