Life is in fact a very rare phenomenon, despite the fact that it surrounds most of us (in no small part with the “rest of us”). You might think it to be common, but that is because you are a part of the commonality of it all. Life is not common – outside of our planet, where it is common.
Some points about the rarity:
- The Earth is in the “Goldilocks Zone” (GZ) which means that it is at the right distance to be “not too hot and not too cold” for life. This is a well-known and rather trite fact to quote, but nevertheless true. Depending on who you ask, the planets Venus and Mars are also in the GZ but apparently lifeless, thus far.
- The Earth is thought to have its relatively fixed spin axis because of the stabilizing influence of the moon. Other planets, without such large satellites are known to have violent shifts in inclination making environments hostile to life. Mars has been suspected of major axial shifts on a short (geological) time scale, for example. Such a large satellite (relative to the planet it orbits – its “primary”) is a very rare condition and the only other example in the Solar System is the Pluto / Charon double planet. And that planet -while extremely spin-stable, is way to Hell and Gone outside the GZ.
- Neither Mars nor Venus has a magnetic field like that of Earth which protects life from massive Solar and Cosmic radiation. It turns out that little Mercury does have a global magnetic field, but it’s hot dry surface is covered by a pitiful excuse for an atmosphere with not much more than vanishing small amounts of hydrogen and helium. And the bare, igneous rocks of Mercury are basking in the glaring sunlight that is more than four times as intense as that experienced by Earth.
- The stable, near circular orbits of the planets that are common in our solar system are not so common in detected planets around other stars (Exoplanets).
- We have studied the Solar System extensively and know at least that conditions for life are extremely rare and Life has not yet been shown to exist anywhere else but on our own Earth.
- It stands to reason that intelligent life is even more scarce. I submit to you that it is so rare as to be vanishingly small.
When Dinosaurs Ruled the Earth
When I was young (that was back in the Cretaceous Era when dinosaurs ruled the Earth), very little was known of what lay beyond that same Earth, even within our own Solar System. It was thought that conditions for Life probably existed on Venus and almost certainly on Mars.
Seasonal changes on Mars that we now know to be dust patterns were taken as sure signs of life. We are now accustomed to sharp clear images of the planets thanks to space probes and extensive image processing of telescope photos. What was available in the early Sixties was not much more than grainy, very low-resolution pictures. As far as Mars was concerned, the expectation of life there was still active right up until the first fly-by images came from Mariner 4 on July 14, 1964.
Those images showed a moon-like, crater-covered surface and the atmosphere was confirmed to be a vanishingly thin layer of carbon dioxide. Those who had held out hope for life on Mars were bitterly disappointed. I know because I was there and this was not at all what I had been led to expect. I am not pointing fingers, you understand. Virtually everybody – scientists included – expected to see something like the early images of desert areas of Earth from space – with, maybe, some cactus plants (roadrunners and coyotes optional). But, these Doses of Reality really were indistinguishable from the airless, lifeless moon and a bitter disillusionment to all. It happened that Mariner 4 did not see the more interesting parts of Mars that later restored some (diminished) hope for life when Mariner 9 images began to arrive.
Probes to Venus sent back even worse news. Cloud-covered Venus had been expected to be a very warm, rainy, damp or perhaps ocean-covered place. All of those scenarios were explored in stories and novels, back in the Golden Age of Science Fiction. If that “Golden Age” phrase puzzles you, go and read these authors: Heinlein, Azimov, Clarke and Bradbury.
Earth observations had already begun to indicate harsh conditions. Measurements from probes revealed that planet to be a quite literal “Hell-hole” with a hot, thick, dry and “crushing” atmosphere that could melt lead. Liquid water – long thought to be a Life “prerequisite” is just a busted myth on Venus.
While Jupiter does possess a magnetic field, it is also surrounded by intense belts of radiation that are trapped in that field. In this regard, I have found some quotes that throw doubt on the chances of hospitable environments on Jupiter’s moon Europa – long thought (after the Voyager probes, that is) to be a good candidate for life.
Some of those doubts:
A Probe called Pioneer 10 was actually the first to encounter Jupiter and there was some concern about radiation levels:
“The level of radiation at Jupiter was ten times more powerful than Pioneer’s designers had predicted, leading to fears that the probe would not survive; however, with a few minor glitches, it managed to pass through the radiation belts, saved in large part by the fact that Jupiter’s magnetosphere had “wobbled” slightly upward at that point, moving away from the spacecraft. However, Pioneer 11 did lose most images of Io, as the radiation had caused its imaging photo polarimeter to receive a number of spurious commands. The subsequent and far more technologically advanced Voyager spacecraft had to be redesigned to cope with the massive radiation levels.” (Magnetosphere of Jupiter, n.d.)
And then there was this, which hammered fifteen more nails into the Europa/Life Coffin::
“The radiation level at the surface of Europa is equivalent to a dose of about 5400 mSv (540 rem) per day, an amount of radiation that would cause severe illness or death in human beings exposed for a single day.:
- The Effects of Nuclear Weapons, Revised ed., US DOD 1962, pp. 592–593
You might argue that there is a “Goldilocks” Zone deep under Europa’s Ice in a Salty Sea of liquid water. Probably more liquid water than on all of the Earth. The miles of ice and water might well protect from radiation. The idea that life could exist there is reasonable, but completely unproven. But is that someplace you want to spend your retirement?
There was also a very thorough work on the radiation dose expected for Apollo astronauts while passing through the Van Allen Radiation Belts (VABR) on the way to moon landings. It concluded that the dose of radiation was relatively tolerable – mostly because the men did not spend much time there.
So far, places where Earth-like conditions exist are: Earth.
- Almost all “Environments” off-Earth are without significant atmospheres, with way too much atmosphere or under miles of ice, submerged in salty seas.
- Many “Environments” off-Earth also tend to be radioactive enough to kill you in a day or two.
- None of these so called “Environments” has actually been shown to harbor any kind of life.
- In every case, these are places that many adventurous people would like to visit. But, without bringing along a complete life support system with you – including when you are “out for a walk” – they are no place you could “live”.
And Then We Get to Titan
Titan is the largest moon of Saturn. It is the third largest moon in the Solar System and larger than planets Mercury and Pluto. And it is just lousy with Earth-like qualities. It has a very dense atmosphere that exceeds the Earth’s sea-level pressure by about 50%.
This first image is pretty much what Voyager 1 saw during its pass by Saturn, arranged especially to look at Titan. It has been known that Titan has an atmosphere since that fact was discovered by Gerald Kuiper (rhymes with “hyper”) in 1944. It became obvious then that to see under this veil of clouds would require more than the cameras aboard the twin Voyager spacecraft. Mostly for that reason was Voyager 2 was cleared (after the successful encounter of Voyager 1 with the satellite) to ignore Titan and continue on a trajectory that would take it to Uranus and Neptune. Had Voyager 1 failed at Titan, Voyager 2 would have followed its brother out of the plane of the Solar System, never having had the opportunity to see the last two Giant planets Uranus and Neptune. Titan got such priority because of its atmosphere which is unique for satellites of any planet.
This second image is from the later Cassini probe that was sent to orbit Saturn and (knowing what Voyager could not see) included an infrared camera which – with some filtering -could see down to the Titanian surface.
While there have been many learned speculations that an exotic form of life might exist that “breathes” hydrogen and exhales methane and “eats” acetylene, none has as yet been detected. “Conventional” Life-as-we-know-it (LAWKI) does these things with oxygen, carbon dioxide and glucose, respectively.
There are indeed Methanogens (i.e., Life that makes methane) on Earth but all of them use liquid water as their “solvent” and none use hydrocarbon liquids as would be the case for the imagined Titanian lifeforms.
I have found no references that indicate the radiation environment is a problem at Titan. This large moon of Saturn is expected to have a subsurface ocean as Europa is thought to have, with the same speculations of “conventional” lifeforms and the same problems to be expected.
Titan is covered with hydrocarbons. These are compounds of hydrogen and carbon that would be called “petroleum” here on Earth. Methane rains down out of the atmosphere and heavier hydrocarbons – solids at that temperature – cover much of the surface resembling sand dunes. These “organic” compounds that have that name because they are -on Earth at least – generally made by lifeforms. I have not read any speculations that Titan’s organics are life-generated.
Titan by virtue of its distance from the sun to Saturn (being 10X that for Earth) receives sunlight arriving there at one percent of what the Earth enjoys. The cloud cover that Titan is notorious for reduces that to one tenth of one percent. Photosynthesis would seem very unlikely. That contributes to a big problem with the idea of Life on Titan. Namely, the temperature, which is so very cold (call it -200 F) that liquid water is decidedly out of the question.
There are, in fact “Great-Lake-size” bodies of liquid on the surface, but they are composed of mostly methane (CH4) – which on Earth is the main component of what’s called Natural Gas. As mentioned earlier, methane is a minor component of Titan’s atmosphere, just as water vapor is in our own Earthly atmosphere and it precipitates to the surface like same.
That would seem to wrap it up for extra-terrestrial life. Several possibilities for environments which show a potential for life, but no evidence that such life exists.
Whatever lifeforms we see fit to deposit…
(from Star Trek II, The Wrath of Khan, in reference to the “Genesis Project”)
Titan’s atmosphere is composed of mostly nitrogen with about 5% methane near ground level with a trace of free hydrogen. While Earth’s atmosphere is similar, being 80% Nitrogen – the remainder consisting mostly of Oxygen with a few trace gasses. Again, the ground-level air pressure exceeds that which you are currently experiencing – even as you read.
This makes Titan is the only place where walking around outdoors without a space suit might be possible.
There are a few problems with that idea, though.
- Titan is extremely cold and would require the Walker to bundle up in arctic gear. Heavy-duty arctic gear.
- This Pedestrian would be breathing from an air tank – like a SCUBA diver. There is no free oxygen in the atmosphere. Let’s say that you use a re-breather and don’t exhaust any oxygen into the atmosphere. Probably best considering the methane.
- That methane (known to drizzle out of the haze you see in the distance) might require a raincoat over all that arctic gear. I doubt you would want to be soaked with evaporating methane when you go inside – where you will definitely have oxygen around.
- The ground where the Huygens probe landed was described as comparable to wet clay. I can’t vouch for the stability or traction achievable on such a surface. Water ice would not be a problem, since at that temperature it is indistinguishable from rock. But those hydrocarbons that cover the surface are much closer to their melting points and could pose a slip hazard. Other places – who knows?
- Don’t let the picture fool you, it will be dark. That photo was taken with a sensitive research instrument. Remember that Titan orbits the planet Saturn, which is ten times as far from the Sun as the Earth. Only one percent of Earthly sunlight reaches Titan and only one tenth of that is able to penetrate the clouds. A moon-lit night on Earth might be the very best level of illumination you could expect.
- You would need artificial lighting, especially through the roughly eight days of darkness when the sun is below the local horizon.
- That brings up electrical generation. Solar panels would be useless in the dimly lit haze. While fierce winds were measured during the descent of Huygens through the atmosphere, surface winds are likely to be intermittent and not particularly strong. So, you won’t want to depend on windmills for power. The probe was powered by batteries, which died after about 90 minutes. No, you will be taking your own power supply to Titan and it will be nuclear in nature – something like a radio-isotope generator. Every probe that made it past Jupiter yet has used such “nukes” for power.
Indigenous Life in the Solar System – once thought so likely – has been shown to be non-existent as far as we know. This is despite decades of intense research toward finding such life.
There is not much to offer for Human occupation “off-Earth” , either. Unless you want to live life completely indoors, surrounded by radiation shielding or in a space suit (much like being “indoors”) Titan is pretty much it.
Having found this one special second place in the Solar System where some semblance of normal human activity is indeed possible, the list of activities is rather short. You won’t be farming. Astronomy is out, but if you happen to be on the side of Titan that faces Saturn, that ringed planet might be barely visible through the haze. Hiking is good and there might be some spectacular landscapes (not at the Huygens landing zone, I’ll admit). Night-vision goggles might be appropriate.
There is one aspect might make it all worthwhile. Titans gravity is a bit less than that of our Moon. About 1/6th of Earth. That combined with the thick atmosphere should make human-powered flight possible. Not just possible, but easy! Even if all your cold-weather clothes, SCUBA gear and “wings” weigh as much as you do, you would still have only one third of your weight on Earth.
There is a sub-culture of misinformed people who think that Humanity’s only salvation will be to move to “another planet”. These folks tend to be against things like fossil fuels and nuclear power. Ironically, if Titan (about the best you can find) is your “other planet”, you will be surrounded by petroleum and using nukes for electricity – in bitter cold and perpetual (more-or-less) darkness.
But you could fly!
Ex Scientia, Veritas,
Star Trek II quote: “Instead of a dead moon, a living, breathing planet, capable of sustaining whatever lifeforms we see fit to deposit on it.” – Dr. Carol Marcus
Van Allen Belt Radiation: http://www.braeunig.us/apollo/VABraddose.htm
Mars Axis instability: https://www.nasa.gov/mission_pages/msl/multimedia/pia15095.html#.WmOspainHIU
Venus (Venera): https://en.wikipedia.org/wiki/Venus
Radioisotope generator: https://www.jpl.nasa.gov/news/fact_sheets/radioisotope-power-systems.pdf