Does Life Exist Elsewhere?


Whatever happened with that news last year about finding life on Venus? Something about phosphine, whatever that is.

And what about the cigar-shaped space rock with the unusual name (Oumuamua) they found in 2017 and called an “interstellar visitor”? Aliens, right? Where’s the follow-up on that?

The shortest, simplest answer to both these versions of the Big Question is that scientists are working on it.

Their scientific method is a very useful tool for getting to the root of things, but it takes time. Too, jargon and the technical details involved do not make for reader-friendly stories.

That’s why journalists usually wait for results to be announced in simple language.

Many years can pass in between press conferences. And sometimes other research teams come up with different results in the meantime, which the journalists also must report.

“…the launching of this ‘bottle’ into the cosmic ‘ocean’ says something very hopeful about life on this planet.” — Carl Sagan via Wikipedia.

This extended, open-ended process generally leaves us laypeople feeling confused and a little put off by Science — except when the topic is “Life Out There.”

THAT always gets our attention.

It appeals to our gut feeling that, if humanity keeps searching long enough, we’ll find ET someday, looking back at us and glad to discover that it’s not alone in this huge universe.

Is that a valid hope or are we just projecting our social selves onto the cosmos?

Alien life isn’t impossible

I’ve found out something cool while reading through the sources for this chapter of the series on how cats evolved.

Painstaking efforts by the world’s top brains have not yet completely ruled out the possibility that there could be extraterrestrial life somewhere.

While probably unintelligent from our viewpoint (NASA, 2021d)), it might be able to hitch a ride through the galaxy to reach our neighborhood!

Of course, boffins haven’t confirmed this.

And whether ET, if it exists, has gotten here is a whole other question.

But such a journey is at least astrophysically possible when rock shields the hypothetical little space tourist from deadly UV radiation and cosmic rays. (Wesson)

I know: Oumuamua, right?

A meteorite found in Algeria. (Image: H. Raab via Wikimedia


Well, probably not. Wesson was writing seven years before that was discovered.

He also described the organism’s protection as a fairly thin rocky layer — the surface of a meteorite, for instance — not something that might be almost as big as the International Space Station (but not shaped like the ISS).

We’ll get to the arguments scientific debate over Oumuamua later on.

Pick-up or delivery? (Image: BolshieBufera/Shutterstock)

For now, let’s just ponder the delightful possibility that a common ancestor of cats and all other life on Earth really might have arrived from space very early in our planet’s history. (Walker et al., 2017b; Wesson)

This isn’t sensationalism: some of the best minds on the planet are discussing it (although they focus on chemistry, physics, and microbiology processes, not cats).

You see, they’re stuck with a couple of major problems that finding ET might help them handle:

  1. There is a mysterious gap in Earth’s fossil record.

    Using a little ingenuity (including “molecular fossils” described in the last chapter), paleontologists have traced Life back slightly more than 3.5 billion years to the Last Universal Common Ancestor (LUCA), whatever that might have been (no one knows for sure, but it definitely existed, perhaps along with other acronym-labeled entities if you subscribe to the hypothesis, which is too complex to get into here, that viruses were also involved).

    Then the rocky archives go blank during the most important part of terrestrial history: Life’s first appearance after young planet Earth had cooled down enough to support it.

    That wouldn’t matter as much if scientists already knew the universal laws on how to turn a lump of matter into Life. (Walker et al., 2017b)

    After all, if you understand how gravity works, you don’t need NASA and the Avengers’ secret test facility (yes) to predict what will happen when you drop a heavy object and a feather in a vacuum):



    But scientists don’t know those universal laws of starting Life yet, because of the next problem.

  2. Astrobiologists have only one sample of life to work with: our own biosphere. (Walker et al., 2017b)

    If they can get one or more additional samples — that is, if Life is found either in the Solar System or on any of the 4,000-plus known exoplanets (those orbiting other stars) — they might then be able to fill in the blank in Earth’s Precambrian archives, or at least to get a better understanding about what might have occurred back then.

So we are looking outwards not only to find ET but also in search of clues to the roots of terrestrial Life here at home.

How did Life evolve?

No one has yet identified geologic evidence that shows the very beginnings of Life on Earth — there are just ambiguous “chemical traces of life” (Gradstein et al.) present in those very old Precambrian rocks.

The Precambrian lasted a lot longer than you might think: it’s everything on this circle except for the blue Phanerozoic, which began with that famous Cambrian explosion of life some 540 million years ago.


This graphic is unofficial and oversimplified. Here’s an interactive version of the real geologic time scale, if you like extreme precision and have the time/mental energy to check out details. (Image: Dimitrios Karamitros/Shutterstock


Yes, we humans are definitely newbies on this world.

A little fiddling with numbers suggests that cats showed up at around 11:55 on that geologic “clock.” Don’t quote me, though; I don’t know what the calculations for it were.

Getting back to the Precambrian, those purple Archaean and green Proterozoic parts are Precambrian eons.

“Hadean” (red) is an informal name for the fiery, chaotic first billion years after Earth (and the rest of our Solar System) formed.

As you can see, microbes ruled for much of the planet’s history, but the clock is a little off regarding their early history, which is controversial.

It’s not shown on this graphic, but the first microbe fossils only show up some 500 million years — in the Archaean eon — after Hadean conditions had presumably sterilized the new world.



“Have a nice da–” — Possible Hadean Life v. 1.*.

“Pow!” — The Universe.

Please also note that having the Moon might have improved chances for early life here on Earth.


To fix the clock:

  • Imagine a span that’s a little shorter than the blue part, in whatever color pleases you
  • Label it “???”
  • Start it at the red/purple line. It ends about a third of the way up the Archaean, at roughly 3.5 billion years.

    Today, tourists in Australia can visit a stromatolite pool. (Image: Benny Marty/Shutterstock)

    That’s where the “microbes” line should begin, where the oldest known fossils are found — 3.5-billion-year-old cyanobacteria that were already advanced enough to resemble their modern descendants, which are also known as stromatolites.

    Everything before those fossils is just speculation.

Some experts, including Cronin and Walker and Walker et al. in the source list, have a problem with the implications of all this: that inert matter became alive in less time than it has taken Phanerozoic life to evolve from simple shelled critters on a Cambrian sea floor to dinosaurs and, more recently, cats, people, and many other beings.

Yet they can’t deny that apparently Earth was just geology (rocks and volcanism), water, and chemicals at one moment, and then seemingly at the next moment, there were energetic things around that could reproduce and evolve — Life, in other words.

The scientists get very technical about this — lots of papers discuss arcane things like polymers, biomolecules, nucleic acids, and the like.

In plain language, it’s as though you added some sugar to a glass of water, stirred it to energize the usual chemical reactions that dissolve sugar, and when the water cleared, there was a frog sitting in that sugar solution.

Where did that come from?

The chemical and/or physical processes we’re aware of just can’t explain the appearance of those first living cells that gave rise to LUCA and eventually to frogs, along with the rest of the animal kingdom, as well as plants, and the microbe domains known to Science today as Bacteria and Archaea. (Walker et al., 2017b)

Steve Corey, CC BY-ND 2.0

I know, I know.

Something along these lines can’t be ruled out, either.

Those of us who have a faith, or who even think about such things, sense a general truth in something Gilbert Chesterton wrote a long time ago in “The Sins of Prince Saradine”:

…[W]e here are on the wrong side of the tapestry…The things that happen here do not seem to mean anything, they mean something somewhere else.”

And we seek out spiritual answers to explain it all.

Unfortunately for boffins, the scientific method doesn’t allow for metaphysics.

Gorodenkoff/Shutterstock

Facts! Nothing but irrefutable facts!

These aren’t easy to collect for something so intangible as Life, especially on a 4.5-billion-year-old planet whose geological record keeps getting reworked and/or erased by plate tectonics.

But scientists have been giving it their best shot for several centuries now.

That is of considerable worth, whatever one’s personal view of Life, the Universe, and Everything might be, if only because they’ve invested so much brain power, effort, wealth, and ingenuity.

If they’re wrong, they’re wrong. But there are several scientific hypotheses about how Life on Earth began (see some references at the end of this chapter, though it’s all very technical).

I’m using Walker and Walker et al. in this series because everyone involved is associated with top-notch exobiology research institutions such as Arizona State and the Blue Marble Institute.

Also their work is highly cited, though not everyone agrees with all their arguments, of course.

Most importantly, from this layperson’s perspective, they sum up possible solutions to the life origin issue very simply and directly:

  1. Life is older than the Earth: it arrived here from space shortly after the planet formed, via meteor strike or some other impact.

    If this hypothesis, called panspermia, is correct (a big “if”!), that means that extraterrestrial life is out there somewhere.

    All we have to do is find it and/or clear-cut evidence that it existed in the past.

    And so, as just one example, we’ve sent the Perseverance rover on a mission to poke around what was once a Martian river delta, billions of years ago.

    Such exploration is also helpful if the second hypothesis proposed by Walker et al. is correct.

  2. Life did evolve here relatively quickly, almost as soon as young Earth was ready for it. If it’s that easy to get going, then extraterrestrial life probably is common, perhaps existing on all Earth-like exoplanets.

    But if that’s true, then what about life in our own Solar System?

Well, water bears now rest in suspended animation on the Moon, but that’s our “oops.” (It does, however, show how rugged Life can be.)

Size comparisons of various Solar System worlds, including some that might host life and the one world that we know is inhabited. (Bluedharma, CC BY-SA-ND 2.0)

There are potential candidates for extraterrestrial life, past or present, on some of the planets and moons orbiting our Sun.

In addition to Mars, the most promising possible host worlds include (NASA 2020a, 2020b; Walker):

  • The planet Venus
  • Saturn’s moon Titan

    The Huygens probe touched down here in 2005. It may look muggy, but Titan is so cold that water ice is as hard as rock.



  • Another Saturn moon, Enceladus
  • Jupiter’s moon Europa

I am just including links here because this is already a long chapter, and we still need to cover the recent newsmakers: Venusian phosphine and Oumuamua, the interstellar visitor.

Besides, all five can be described in comparison to early Earth, which will be covered in the next chapter:

  • Venus is very similar to Earth (except for its current climate!) and might even have been the Solar System’s first habitable world. (NASA, 2021)
  • Earth was once a “pale orange dot,” with an atmosphere like Titan’s but for different reasons. (NASA 2020b)
  • Our home is a rocky planet, but it’s also considered an ocean world like Enceladus and Europa. Indeed, for a while, near the end of the Precambrian, Earth was also icy like those two moons although opinions vary as to whether it was a “snowball” or a “slushball.”

And Mars? Well, apparently, its geology used to look like this:



Now then —

Is there life on Venus?

The second planet from Sun, so similar to Earth in size and mass, is the hottest orbiting object in the Solar System.

Thanks to a runaway greenhouse effect from its dense, cloudy atmosphere of carbon dioxide, and perhaps other factors like volcanism, surface temperatures on Venus are a balmy 700-plus degrees Fahrenheit!

Not that you’d have time to notice the heat if you visited the place — you’d immediately be crushed. Surface air pressure there equals the water pressure found a mile below Earth’s ocean waves.

We know this because a couple of landers reached the ground safely and survived just long enough to send back some data.



What Venus sounds like (the various bumps and rumbles are the Venera 14 lander doing its thing).


But Venus is still possibly a host for extraterrestrial life because temperatures and air pressure are milder, high up in the clouds.

NASA/JPL-Caltech

ET conceivably could exist at these altitudes, if it could get by without water and handle lots of sulfuric acid, which is what those clouds are made of.

That’s another very big “if.” Most searches for alien life “follow the water” since it is so necessary for life as we know it.

Still, there are extremophiles on Earth that thrive in very hostile environments. And let’s not forget those durable lunar water bears.

Intriguingly, there are permanent dark streaks and reddish smudges visible in cloud tops on Venus. Nobody knows what some of these are, but microbial life is one — just one — of the potential explanations.

Now, about that phosphine discovery.

In brief (Dunham; NASA 2021, 2021a; O’Callaghan; and Witze):

  • Phosphine is a hydrogen-phosphorus compound that’s highly toxic to us. On Earth, it’s produced by bacteria in oxygen-starved places like sewage treatment plants and certain natural sites, like swamps.
  • In September 2020, researchers using the James Clerk Maxwell Telescope in Hawaii and the ALMA radio telescope in Chile announced that they had detected trace amounts of phosphine high in the sulfuric acid clouds of Venus. It really shouldn’t be there, given that planet’s hellish conditions, and the team came up with several possible explanations. They had to include the sensational explanation — life — along with purely chemical hypotheses, because it isn’t impossible that microbes there might be producing phosphine faster than Venus can destroy it.
  • Naturally, scientists around the world were on this like white on rice. It quickly came to light that the ALMA observatory had processed its data incorrectly. They did it again correctly, and everyone, including the original team, repeated the experiment. Some researchers reported finding no phosphine, but the original team still insists it is there.
  • Most recently, yet another group announced that the “phosphine” was actually SO2 from explosive volcanism (which itself has yet to be confirmed on Venus).
  • The argument will likely go back and forth until new data come in, perhaps from upcoming Venus missions planned by NASA and the European Space Agency in a few years. (Japan has had a spacecraft orbiting Venus for a few years now, but it’s designed to study Venusian weather and climate, not to sniff out phosphine or other traces of life.)

Oumuamua

It’s that little dot. (Image: NASA; Alan Fitzsimmons (ARC, Queen’s University Belfast), Isaac Newton GroupDerivative: nagualdesign; via Astronomy Picture of the Day)

Oumuamua is easier to discuss because so very little is known about it.

Most of us don’t realize that the cigar-shaped object shown in news stories was just an artist’s interpretation of an object so far away that it looks like a dot in telescopic views.

Its true shape might be quite different.

It was first thought to be a comet, but astronomers could detect no tail of particles. The possibility if its being an asteroid was discussed, but Oumuamua’s speed made most experts decide it was an interstellar object of some type.

Here is a description from the first full review of this strange obect:

‘Oumuamua is red, similar to many Solar System small bodies, e.g., comets, D-type asteroids, some Jupiter Trojans, and the more neutral trans-Neptunian objects…While the color is consistent with organic-rich surfaces, it is also consistent with iron-rich minerals, and with space weathered surfaces. Thus, color alone is not diagnostic of composition…‘Oumuamua exhibited short-term brightness variation of over a factor of ten (>2.5 magnitudes)… The brightness range was unusually large…While brightness variations can be due to variations in the viewing geometry of a particular shape, or due to patchy albedo across a surface, minor planets’ light curves are usually assumed to be shape-dominated, as their surfaces are thought to be covered by small regolith that is evenly distributed across the surface…How we interpret the shape of ‘Oumuamua depends on its specific state of rotation, including its rotation pole [which isn’t known — BJD]. ‘Oumuamua can either have a narrow elongated-ellipsoid shape or a shape more reminiscent of a flattened oval…As the first interstellar visitor to our solar system, ‘Oumuamua has challenged many of our assumptions about how small bodies from another star system would look. While ‘Oumuamua presents a number of compelling questions, we have shown that each can be answered by assuming ‘Oumuamua to be a natural object. Assertions that ‘Oumuamua may be artificial are not justified when the wide body of current knowledge about solar system minor bodies and planetary formation is considered.

That’s apparently the official position on Oumuamua.

There are other opinions, though.

For example, Dr. Avi Loeb, a well-known and respected astronomer, writes in Scientific American that “the interstellar object discovered in 2017, ‘Oumuamua, was inferred to have a flat shape and seemed to be pushed away from the sun as if it were a lightsail.”

He goes on to wonder “if ‘Oumuamua was an artificial object on a targeted mission towards the sun, aimed to collect data from the habitable region near Earth. One might even wonder whether ‘Oumuamua might have been retrieving data from probes that were already sprinkled on Earth at an earlier time. In such a case, ‘Oumuamua’s thin, flat shape could have been that of a receiver. Hence, ‘Oumuamua was pushed by sunlight not for the purpose of propulsion but as a byproduct of its thin flat shape. A similar push by reflection of sunlight without a cometary tail were the traits of an artificial rocket booster that was identified in 2020 by the same Pan-STARRS telescope that discovered ‘Oumuamua. This artificial object named 2020 SO was not designed to be a solar sail but had thin walls with a large surface-to-mass ratio for a different purpose.”

This whole debate is way above our pay grade, and unfortunately there’s no Star Fleet cruiser available to hunt down Oumuamua and learn what it is.

So we’ll just have to wait for ET to phone again or for Chance to send another space rock, if that’s what Oumuamua is, tumbling past us at a safe distance. Perhaps by then we will have the technology to see it clearly, as well as to collect more data on it.

Meanwhile, let’s continue to follow the sage advice of that 1950s philosopher who said:




Featured image: Andrey_F/Shutterstock


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Avnir, D. 2020. Critical review of chirality indicators of extraterrestrial life. New Astronomy Reviews: 101596.

Corsetti, F. A.; Olcott, A. N.; and Bakermans, C. 2006. The biotic response to Neoproterozoic snowball Earth. Palaeogeography, Palaeoclimatology, Palaeoecology, 232(2-4): 114-130.

Cronin, L., and Walker, S. I. 2016. Beyond prebiotic chemistry. Science, 352(6290): 1174-1175.

David, V. A.; Menotti-Raymond, M.; Wallace, A. C.; Roelke, M.; and others. 2014. Endogenous retrovirus insertion in the KIT oncogene determines white and white spotting in domestic cats. G3: Genes, Genomes, Genetics, g3-114.

Dunham, W. 2020. Potential sign of alien life detected on inhospitable Venus. https://www.reuters.com/article/space-exploration-venus-int/potential-sign-of-alien-life-detected-on-inhospitable-venus-idUSKBN2652GI Last accessed July 12, 2021.

Durzyńska, J., and Goździcka-Józefiak, A. 2015. Viruses and cells intertwined since the dawn of evolution. Virology Journal, 12(1): 1-10. https://link.springer.com/article/10.1186/s12985-015-0400-7

Guttenberg, N.; Virgo, N.; Chandru, K.; Scharf, C.; and Mamajanov, I. 2017. Bulk measurements of messy chemistries are needed for a theory of the origins of life. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 375(2109), 20160347.
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Kirschvink, J. L., and Weiss, B. P. (2002). Mars, panspermia, and the origin of life: where did it all begin. Palaeontologia electronica, 4(2): 8-15.

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Lingam, M., and Loeb, A. 2018a. Is extraterrestrial life suppressed on subsurface ocean worlds due to the paucity of bioessential elements?. The Astronomical Journal, 156(4): 151.
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___ 2018b. Implications of captured interstellar objects for panspermia and extraterrestrial life. The Astronomical Journal, 156(5): 193.

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NASA. 2020a. Can we find life? https://exoplanets.nasa.gov/search-for-life/can-we-find-life/ Last accessed July 12, 2021.

___. 2020b. Life in our Solar System? Meet the neighbors. https://exoplanets.nasa.gov/news/1665/life-in-our-solar-system-meet-the-neighbors/ Last accessed July 12, 2021.

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___. 2021b. Venus overview. https://solarsystem.nasa.gov/planets/venus/overview/ Last accessed July 12, 2021.

___. 2021c. The searchers: How will NASA look for signs of life beyond Earth? https://exoplanets.nasa.gov/news/1681/the-searchers-how-will-nasa-look-for-signs-of-life-beyond-earth/ Last accessed July 12, 2021.

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___. n.d.(a) Europa Clipper: Ingredients for life. https://europa.nasa.gov/why-europa/ingr.edients-for-life/ Last accessed July 12, 2021

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