How can we search for life on icy moons such as Europa?

November 24, 2014 by Elizabeth Howell,,
Artist’s conception of water vapor plume erupting from the icy surface of Europa, a moon of Jupiter, based on data from the Hubble Space Telescope. Credit: NASA/ESA/K. Retherford/SWRI

Our solar system is host to a wealth of icy worlds that may have water beneath the surface. The Cassini spacecraft recently uncovered evidence of a possible ocean under the surface of Saturn's moon, Mimas.

Mimas is not alone in the possibility of having a global ocean, which would potentially provide a foothold for life to exist. Other worlds under examination include Jupiter's moon, Europa. In 2013, NASA's Hubble Space Telescope observed evidence that Europa erupts water, while the Cassini spacecraft has observed geysers spewing on Saturn's moon, Enceladus.

How likely is habitability on such icy worlds, and how would we search for it? This is one of the questions driving a research team led by Isik Kanik at NASA's Jet Propulsion Laboratory in Pasadena, California. Kanik's team was selected for a new grant from the NASA Astrobiology Institute for a five-year project looking at how metabolism could come about by way of chemical differences on icy worlds, and how signatures of these unbalanced states can be detected. This is assuming that metabolism works similarly on these other worlds as it does on Earth.

One of the ways Kanik's team will look for these signatures is to use analog environments on Earth. These are locations that scientists believe are similar, in certain respects, to what could be present on other worlds. In theory, life on another world could evolve from a chemical soup similar to that of certain places on Earth, such as within hot springs.

The Cedars, in California, and Cabeco de Vide, in Portugal, host natural springs that represent two extreme metabolic environments, with energy sources produced by water-rock interactions and particular types of organisms that find a way to take advantage of them, Kanik said.

"The sites are accessible field analogs to deep-sea hydrothermal systems on Earth's seafloor, which are very costly to explore. These are life-supporting environments similar to those that could exist on Europa or early Mars, Kanik said.

Moving life from vents to the surface

Members of Kanik's group have been at work with some of their research for decades, long before astrobiology was considered a distinct study of its own. This is their second grant with the NASA Astrobiology Institute; the first proposal, selected five years ago, focused on how life could have emerged from hydrothermal vents in the ocean.

"That's important because NASA is considering sending a spacecraft to Europa," Kanik said. "If they go and look for signatures of life, how are they going to interpret findings of organic molecules? That was the basic driver."

Saturn’s moon Enceladus spews water vapor and ice particles from fractures in the ice. Scientists have found about 100 of these geysers. Credit: NASA/JPL-Caltech/SSI

Another major part of the research was modeling how life could evolve in the laboratory environment. Championed by the NASA Astrobiology Institute's Michael Russell, the sub-team set up experiments in a hydrothermal reactor in the laboratory using simulated ocean water, some , and then "mixing them and looking at what comes out," Kanik said.

The team produced about 250 papers based on their work over five years, he noted. Among the major milestones:

How life came to be in icy worlds

The new research focuses on four questions that are related to the possible emergence and evolution of life in icy environments, particularly in locations in the Universe such as Europa, Enceladus and Jupiter's moon Ganymede.

The first question asks, "What geological and hydrologic factors drive chemical disequilibria at water-rock interactions on Earth and other worlds?" The researchers will conduct laboratory experiments and field investigations to understand more about the chemistry, including factors such as acidity and electrochemistry.

"There are three basic ingredients for life to emerge: water, free energy and chemicals. Chemical reactions need to keep happening in one direction or the other—either using or giving off energy," Kanik said.

"As soon as reactions reach equilibrium, there is no energy to be used or made available. Therefore, once the system reaches equilibrium, nothing happens. So chemical disequilibrium is necessary for life to emerge."

NASA’s Juno mission, slated to arrive at Jupiter in 2016, will have the agency in the neighborhood of icy Europa for the first time since the Galileo mission of the 1990s and early 2000s. Credit: NASA/JPL-Caltech

A part of the investigation will involve going to geological field sites in California and Portugal using portable scientific instruments that were developed through past NASA funding. Under the first Icy Worlds project, team members Lance Christensen and Steve Vance have been developing tunable laser spectrometers (TLS) to investigate methane and other small molecules produced by serpentinization. The JPL TLS instrument on Curiosity, part of the Sample Analysis at Mars package, has been used on Mars to analyze elements in rocks and in the atmosphere as the Curiosity rover searches for ancient habitable environments at its main science destination of Mount Sharp (Aeolis Mons).

"We are going to take them to these sites and look at what kind of gases come out, and analyze the water and gases from these places," Kanik said. "We'll take some samples and bring them to the lab to make sure we have done it correctly."

The team also has a laboratory experiment to investigate serpentinization as it might have occurred on the early Earth before life emerged. This system provides a comparison of the natural sites where biology is present, allowing the team to understand the interaction between chemistry and biology.

The second question asks whether geo-electrochemical gradients—changes in geology and electrochemistry—in can eventually create chemistry that leads to . Using fuel cells, the investigators will simulate how a vent system works, with the aim of understanding how they would behave on icy worlds.

How can we search for life on icy moons such as Europa?
Many scientists believe that life on Earth arose from the oceans, making it possible for this same process to work on icy moons such as Enceladus or Europa. Credit: NASA

Third, the research team will ask, "How, where and for how long might disequilibria exist in icy worlds, and what does that imply in terms of habitability?" This will involve making models of how seafloors may be different on icy worlds due to to factors such as temperature and pressure.

The fourth question asks, "What can observable surface chemical signatures tell us about the habitability of subsurface oceans?" Again, simulations will take place of icy bodies, including factors such as a vacuum, radiation and the appropriate surface temperatures. The aim here is to link what is seen on the surface with what is happening below.

While the exact budget has not been established yet for Kanik's team, on average the research groups awarded funding in this round received $8 million each. Kanik said the research will not only support dozens of scientists, but also provide extensive training for both graduate and undergraduate students training to become professional astrobiologists after graduation.

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5 / 5 (1) Nov 24, 2014
The article is about how to search for life on these icy worlds, not about how to prove abiogenesis. With the large number of assumptions already being made, I'd be surprised if they recognized any life that is there if they found it. For now, why not forget about trying to imagine how anything might have "evolved" there and just find it first. Once you've found the life, then you can go ahead and write all kinds of papers, speculating about what might have happened millions or billions of years ago. However, speculation is not science, no matter how erudite it is. Get real data first, and don't start with so many assumptions. No one has been able to produce life via abiogenesis or spontaneous generation, and even if it is possible, it should take millions or billions of years, not a practical time frame for scientific experimentation.
not rated yet Nov 24, 2014
A sometimes-overlooked persistent disequilibrium is any sort of temperature gradient. Given tidal heating in jovian moons, temperature gradients are a certainty.

I am vaguely remembering a science fiction story, not recent, in which a category of life is proposed for jovian moon-oceans which literally feeds itself on heat energy as it moves on the gradient. Feasible? Maybe. We can harvest temperature gradients to produce electricity - not commercially, yet, but it's possible to do it.

I can't imagine how a NASA probe could get through a kilometer of ice. I suppose we'll have to investigate active or recent vents to look for organic detritus.
not rated yet Nov 24, 2014

Regardless of whether it emerged there or arrived via panspermia, the issues being addressed here are how it would have developed since its inception, and thus what to actually look for, and where.

The time frame required for abiogenesis is neither here nor there...
not rated yet Nov 25, 2014
@Urgelt: We did a survey in an astrobiology course, and thermal gradients were among the too diffuse ones that they would be used. And we can see that current life do not do so, meaning it is hard or impossible to evolve.

Re detection, hopefully the Europa vents can be confirmed. Else they would have to land on fresh ice with the first lander, or eventually drill down to the ocean.
5 / 5 (1) Nov 25, 2014
Too bad for the creationist crackpots showing up that every article they comment on prove that they are wrong. because biology, astrobiology and cosmology works.

And an obvious, glaring creationist mistake here: Re emergence of life, it is already tested. We know from century old cosmology that the early universe was too hot for life. Hence it is an observed fact that life emerged.

Today we even know from phylogenies that they evolved out of geophysical systems, since the associated environmental memory of the gene environment (the cellular machinery and its nutrients) display homologies with submarine systems.

But same as there are still people claiming having invented perpeetum mobiles every year, expect creationist trolls to continue spout lies about known biology. It's a good witness to their desperation, it used to be they could claim ignorance. Now they have to show us how morally corrupt they are. :-/

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