Why Searching for Extraterrestrial Life in the Solar System is Hella Important
“My great disappointment would be going to Mars and finding […] that it would not've been a separate experiment in life.” — Neil Degrasse Tyson to Richard Dawkins (Dawkins & Tyson, The Poetry of Science, 2010, 7:15-7:24 minutes in)
Neil Degrasse Tyson had better prepare to be disappointed, because it’s likely the case that all life in the galaxy is related. It is well-known that meteors may strike the Earth hard enough to kick rocks back up into space, and that these rocks may contain micro-organisms. According to “A mechanism for interstellar panspermia” by W. M. Napier (2003) and “Interstellar transfer of planetary microbiota” by M. K. Wallis and N. C. Wickramasinghe, these rocks may be subsequently pulverized into grains so tiny that Solar winds may carry them out of the Solar system. These grains, though very small, would still be large enough to house whole colonies of microscopic lifeforms and shield them from potentially deadly radiation. As the stars of the Milky Way rotate around the galactic center, these grains would contaminate gas clouds and planetary systems moving through our wake. Napier, Wallis, and Wickramisinghe calculate that the Earth could have seeded the entire Milky Way galaxy with life by such a process in just a few billion years. Considering any Earth-like planet could hypothetically have done the same, it’s extremely unlikely that the Earth is the planet this all started on. It is therefore very likely that any life we might find in the galaxy, no-matter how many tens of thousands of lightyears away, will be related to us. It also means there’s no guarantee that the common ancestor of all life on Earth even lived here on Earth.
Furthermore, while hundreds of tons of Mars rock may have reached Earth over the last few billions years (Tyson, 2016), more than 40,000 tons of space dust rain to Earth each year (Wallis & Wickramasinghe, 2003; Napier, 2003), or about 180 trillion tons over the lifetime of the Earth. This means that the amount of Martian material we’ve received over the history of our planet accounts for mere parts-per-trillion of the total amount of material we’ve receive from space. Consequently, should there appear to be any genetic relationship between life on Earth and any living or fossil organisms discovered on Mars, one or more common third-party (and probably extrasolar) source(s) for life on Earth and Mars would be an overwhelmingly more likely explanation than contamination of one planet by the other.
Currently the main candidates for extraterrestrial life in the Solar system are the clouds of Venus, the Martian subterrain, and the oceans of ice moons like Europa, Enceladus, and Titan. Should we locate extraterrestrial life in any of these venues, the genetic relationships among them and with life on Earth, if any, would tell us a great deal about what was happening during the formation of the Solar system, help us predict what we might expect to find on extrasolar planets, and teach us more about our place in the greater context of biological life.
If we find life here in the Solar system and it is not related to us, then Tyson & Dawkins will have gotten the “second sample of life” (Dawkins & Tyson, 2011) they were hoping for, implying the formation of life is relatively easy and there might be myriad ways in which life might form. However, if we find life in the Solar system related to us, then that would bolster the case that there was a common source of material in the gas cloud that the Solar system formed from and/or that all life in the galaxy is related. This should not be a disappointment at all, but a great source of encouragement! For this would mean that in the coming billions of years, after the Sun goes nova and the Milky Way galaxy collides with our neighboring galaxy, Andromeda, even if life on Earth doesn’t make it, something of our form of life is almost certain to survive.
It’s not a “second sample of life” we should be hoping to find as we continue to probe our Solar system. What we should hope to find is the exact opposite. We should hope that our form of life extends beyond this planet. It already seems likely that will be the case, but the only way to know for sure is to go out there and find some life. It’s imperative that we do. We need to understand our chances of survival.
Dawkins, R.; Tyson, N. D. The Poetry of Science. Richard Dawkins Foundation for Reason & Science. Youtube. October 10, 2010.
Napier, W. M. A mechanism for interstellar panspermia. Mon. Not. R. Astron. Soc. 348, 52-61 (2004). Accepted 2003 October 2. Recieved 2003 October 1; in original form 2003 April 4. doi:10.1111/j.1365-2966.2004.07287.x
Wallis, Max K. and Wickramasinghe, N. C. Interstellar transfer of planetary microbiota. Mon. Not. R. Astron. Soc. 348, 52-61 (2004). Accepted 2003 October 23. Recieved 2003 October 23; in original form 2003 June 5. doi:10.1111/j.1365-292004.07355.x