If We Find Life on Europa or Enceladus, It Will Probably Be a '2nd Genesis'

An up-close look at the "tiger stripes" on Saturn's moon Enceladus, which is thought to harbor a big ocean of liquid water beneath its icy surface.
An up-close look at the "tiger stripes" on Saturn's moon Enceladus, which is thought to harbor a big ocean of liquid water beneath its icy surface. (Image credit: NASA, ESA, JPL, SSI, Cassini Imaging Team)

SAN FRANCISCO — If there are creatures swimming in the buried oceans of the outer solar system, they're probably not related to us, new research suggests.

Some scientists believe that life has hopped from world to world around the solar system, aboard chunks of rock blasted into space by comet or asteroid impacts. Indeed, there's a school of thought that the life teeming here on Earth is actually native to Mars, which likely boasted habitable conditions earlier than our own planet did. (This rock-riding idea is known as "lithopanspermia," a subset of the broader panspermia notion, which envisions spread by whatever means, either natural or guided by an intelligent hand.)

But what are the odds that such putative pioneers could colonize the habitable real estate much farther out — specifically, the Jupiter moon Europa and the Saturn satellite Enceladus, both of which harbor big oceans of salty liquid water beneath their ice shells?

Related: 6 Most Likely Places for Alien Life in the Solar System

Purdue University geophysicist Jay Melosh tackled this question and presented the results last week during a talk here at the annual fall meeting of the American Geophysical Union. 

Melosh used computer models to follow the fates of 100,000 simulated Mars particles launched off the Red Planet by an impact. He modeled three different ejection speeds: 1, 3, and 5 kilometers per second (about 2,240 mph, 6,710 mph and and 11,180 mph, respectively).

In the simulations, a tiny percentage of the particles ended up hitting Enceladus over the course of 4.5 billion years — just 0.0000002% to 0.0000004% of the number that impacted Earth. The numbers were about 100 times higher for Europa; that moon got 0.00004% to 0.00007% of Earth's particle share.

We know that about 1 ton of Mars rocks that are fist-size or larger rain down on Earth every year. Using that figure, Melosh calculated that Europa gets about 0.4 grams of Mars material per year, and Enceladus receives just 2-4 milligrams. These are averages, he stressed; the moons' Mars mass almost certainly comes from very infrequent arrivals of decent-sized rocks, not a steady flow of small stuff.

The numbers are similar if the source of the rocks is Earth rather than Mars, Melosh said.

These results might seem to bode well for life's spread; after all, it might take just one impact of a microbe-bearing rock to turn Europa or Enceladus from habitable to inhabited. But there are more factors to consider, and they tamp down the optimism.

For example, Melosh found that the median transit time for a Mars meteorite that ends up hitting Enceladus is 2 billion years. Microbes are tough, but that's a long time to endure the harsh conditions of deep space. And the simulations indicated that these incoming Mars rocks would hit Enceladus at between 5 and 31 km/s (11,180 mph to 69,350 mph). The lower end of that range might be survivable, but it's hard to imagine anything living through those more extreme impacts, Melosh said.

"So, the bottom line: If life should be found in the oceans of Europa or Enceladus, it is very likely that it’s indigenous rather than seeded from Earth, Mars or (especially) another solar system," Melosh said during his AGU talk. (His calculations peg the probability of an exoplanet meteorite impacting Earth over the past 4.5 billion years at just 0.01%. The chances are much lower for Europa and Enceladus, he said.)

Related: 7 Theories on the Origin of Life

That's exciting news, if viewed from a certain perspective. Europa and Enceladus — and other potentially habitable worlds in the outer solar system, such as Saturn's huge moon Titan — may well have remained uncontaminated for eons, providing ample opportunity for native life-forms to take root and evolve. So, our solar system may boast many different types of life, rather than one widespread one. (Of course, seeing how Earth-like life would evolve over billions of years in a frigid, buried ocean would be pretty exciting, too.)

And if we discover just one such "second genesis" in our solar system, we would know that life is no miracle and must be common throughout the cosmos. 

We may be on the verge of answering some of these profound questions. For example, NASA is developing a mission called Europa Clipper, which will characterize the satellite's ocean and scout out potential touchdown sites for a future life-hunting lander mission, among other tasks. Clipper is scheduled to launch in the early to mid-2020s, but the lander's future is murky; though Congress has ordered NASA to develop the surface mission, it's unclear if the funding will come through to make that happen.

Another NASA mission, called Dragonfly, will launch in 2026 to study Titan's complex chemistry. This robotic rotorcraft could potentially spot signs of life in the big moon's air, if any are there to be found. And over the longer haul, researchers are looking into ways to get a robot through the ice shells of Europa and Enceladus and into their possibly life-supporting oceans. No such mission is on the books, but one could get off the ground in the 2030s if we're lucky.

There will be serious astrobiological action closer to home soon, too. NASA plans to launch a life-hunting rover to Mars next summer, as do the European Space Agency and Russia, which are working together via a program called ExoMars. Both of these wheeled robots will focus on finding signs of ancient, not currently existing, Red Planet organisms. (Of course, chances are decent that Martians, if they exist, are related to us.)

Exoplanets are part of the picture as well. NASA's James Webb Space Telescope, which is due to launch in 2021, will be able to sniff the atmospheres of nearby alien worlds for potential biosignatures, as will three giant ground-based observatories scheduled to come online in the middle to late 2020s — the Giant Magellan Telescope, the Extremely Large Telescope and the Thirty Meter Telescope.

Mike Wall's book about the search for alien life, "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook

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Mike Wall
Senior Space Writer

Michael Wall is a Senior Space Writer with Space.com and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.

  • rod
    Admin said:
    If there are creatures swimming in the buried oceans of the outer solar system, they're probably not related to us, new research suggests.

    If We Find Life on Europa or Enceladus, It Will Probably Be a '2nd Genesis' : Read more

    "These results might seem to bode well for life's spread; after all, it might take just one impact of a microbe-bearing rock to turn Europa or Enceladus from habitable to inhabited. But there are more factors to consider, and they tamp down the optimism."

    There is a critical assumption that is the foundation of all searches for life on other worlds. The well attested law of abiogenesis, this law of science is as well attested as Kepler's planetary laws, Newton's laws of motion, or the law of gravity - thus the law of abiogenesis is operating throughout the universe and in our solar system billions of years ago. I was glad to read some caution in the report. I watched a recent SCI program (How The Universe Works) where molten creatures swim around in a hot, molten sea on some remote, hot jupiter type exoplanet - as a possibility for alien life too.
    Reply
  • Alfa015
    Agreed!
    Btw Exoplanets Telescope Launch: SjYdIKI2DlAView: https://youtu.be/SjYdIKI2DlA
    Reply
  • ZaMan
    If there are reasons to exclude a first genesis happening on a habitable Moon and then migrating to Mars and/or the Earth, these are glaringly absent from the article. This possibility would obviate the need for a second genesis to explain life on a moon of Saturn or Jupiter. It seems a reasonable assumption that the travel time to the inner planets would be far shorter then the trip outward.......
    Reply
  • ZaMan
    Mental Avenger said:
    The intense radiation from Jupiter, within Jupiter’s Magnetosphere, where the 5 larges moons orbit, would eliminate the presence, let alone the genesis, of life there.

    I have not done the math, but since the DeltaV is the same either direction, the energy required could be the same either way.
    I suspect it is way easier and faster to fall in toward the sun's gravity well than to move outward.
    Reply
  • ZaMan
    Mental Avenger said:
    The intense radiation from Jupiter, within Jupiter’s Magnetosphere, where the 5 larges moons orbit, would eliminate the presence, let alone the genesis, of life there.

    I have not done the math, but since the DeltaV is the same either direction, the energy required could be the same either way.
    Not necessarily true. 100 miles of water and ice would provide protection from radiation. If "eliminate the presence of..........life there", then why would we be talking about it, whether by genesis or panspermia?
    Reply
  • Curt
    rod said:
    "These results might seem to bode well for life's spread; after all, it might take just one impact of a microbe-bearing rock to turn Europa or Enceladus from habitable to inhabited. But there are more factors to consider, and they tamp down the optimism."

    There is a critical assumption that is the foundation of all searches for life on other worlds. The well attested law of abiogenesis, this law of science is as well attested as Kepler's planetary laws, Newton's laws of motion, or the law of gravity - thus the law of abiogenesis is operating throughout the universe and in our solar system billions of years ago. I was glad to read some caution in the report. I watched a recent SCI program (How The Universe Works) where molten creatures swim around in a hot, molten sea on some remote, hot jupiter type exoplanet - as a possibility for alien life too.
    As far as I can tell, there is no 'Law of Abiogenesis'. There once was a Law of Biogenesis, but that has been debunked.
    Reply
  • rod
    Curt said:
    As far as I can tell, there is no 'Law of Abiogenesis'. There once was a Law of Biogenesis, but that has been debunked.

    My note here. The law of abiogenesis is the critical assumption behind SETI and all searches for life outside of Earth. The law of biogenesis was affirmed by Louis Pasteur research and studies.
    Reply