New evidence: Comets seeded life on Earth
Simulated cosmic snowball breeds complex organics
Ever since its formation, the Earth has been bombarded by comets, and scientists think they now have evidence that these cosmic missiles could have carried the building blocks for life along with them when they impacted.
In 2009, NASA's Stardust mission rendezvoused with the comet Wild-2 and returned to Earth with a sample of an amino acid the probe had picked up from comet's outgassing. Tests showed it had too much carbon-13 to have come from Earth, but skepticism remains that simple amino acids could have kick-started the development of life on the planet.
To test that hypothesis, a team of scientists at the University of California, Berkeley, and the University of Hawaii, Manoa, built a pseudo-comet in the lab – a snowball of carbon dioxide, ammonia, and various hydrocarbons such as methane, ethane, and propane – then chilled it in an ultra-high-vacuum chamber down to 10 degrees above absolute zero.
The comet was then zapped with high-energy electrons to simulate the cosmic rays it would encounter had it travelled through space. The team then analyzed the result to see what had formed using the Mars Organic Analyzer, an instrument designed for ultrasensitive detection and identification of small organic molecules in the Solar System.
On analysis, the laboratory comet was found to have not only nine different amino acids but also at least two dipeptides – linked pairs of amino acids that are capable of forming proteins (polypeptides), enzymes, and more-complex molecules such as sugars.
"It is fascinating to consider that the most basic biochemical building blocks that led to life on Earth may well have had an extraterrestrial origin," said UC Berkeley chemist Richard Mathies, coauthor of the paper to be published in The Astrophysical Journal, in a statement.
Previous scientific theories have largely revolved around the famous 1953 Miller-Urey experiment, in which simulated lightning was fired into a primordial soup of water, methane, ammonia, and hydrogen. This produced over 20 amino acids, and further research in the area is continuing.
Of course there are still plenty of people – particularly here in the US – who will tell you that humans were created by a supernatural deity (who curiously burdened humans with such useless organs as the appendix and men's nipples) and therefor such scientific research is pointless.
But for scientists, the news is rather exciting. ®
Appendix not useless
Just for the record: the appendix function has been found. Its use is to harbor intestinal flora and to reseed the colon with beneficial bacteria after a diarrhoea. As such, it's either a nice piece of evolutionary work, or another proof of intelligent design, depending upon your axioms.
Given the prevalence of diarrhoea-giving diseases, the appendix probably improves mankind's survival rate. From which you can deduct that death from the aftermath of a cholera-type disease was historically a bigger risk than appendicitis.
Re: God arrived by comet!
Blitzen was having a day off?
Miller-Urey experiment is ongoing
Miller-Urey will probably remain ongoing for at least another century. It is currently under the care of their protege Jeffrey Bada.
Just now we have an interstellar comet called Siding Spring headed toward Mars on a hyperbolic course. The hyperbolic shape of its course and its speed tells us that it cannot be from our solar system and won't be staying unless it hits something. It already has solar system escape velocity, as any mass entering Sol's influence naturally would - an object in motion remains in motion... The coma, or "head" of this comet is almost certain to scatter debris on Mars from its interstellar journey and its distant home. The coma is expected to have a larger radius than the average Mars miss distance. There is no telling how far it has flown but that it is not from here is certain. That coma is a considerable threat to our Mars system assets as to be hit by a flyspeck of something moving 55km/s is outside of worst-case design spec.
As it tracks through about two light-years of sol system's Hill Sphere Siding Spring will naturally pick up material from here - dust and gas from the solar system's creation, bits of asteroid, some microscopic interstellar particles, and debris from asteroid and comet collisions with Earth and Mars. As asteroids have struck Earth since life arose with sufficient force to knock bits of life-bearing matter off, it is likely the comet will scoop up some of that, and it's notable later in this story. It might land on Mars with its full payload, but that outcome is unlikely. If that does happen it will be quite dramatic, blasting up to a 500km crater 4km deep in the surface - roughly 7% of Mars' diameter. That blast has been calculated as up to as much energy as 20 billion megatons of TNT equivalent - on par with a dinosaur killer. You would be able to see it as an increased brightness of Mars unaided by a telescope. Mars would be warm for a while, and all our orbiting and landed science would likely be destroyed - but hopefully they might send back great science and dramatic pictures first.
If it misses Mars and the Martian moons it will not make the grand tour of the major planets. It's coming from off the main plane of the solar system and departs the same way without interacting with any other planet's sphere of influence. Away it will go into the dark carrying with it the mysteries it brought, and a few it picked up here. At some future time it will dispense this bounty throughout another solar system - as comets do, mostly as dust that will fall on all bodies there.
If it misses back into the dark it will go, disappointing thousands of planetary scientists and carrying with it proof that at least the dinosaurs - but not we - were here. There is little chance that it will not fall into another sun's sway some day, collide with an object large enough to break it up, or otherwise end its journey. Space is vast but it's not that vast, and time is long. Over eons Siding Spring's Earthly Life discoveries - barring a Mars hit - will be spread throughout our local group of stars, and over the next billion years spread throughout the Milky Way. Life is unbelievably toxic and persistent, so some fragments of it are certain to fall on fertile ground just from this one comet that we see, let alone the billions that we didn't.
It's likely that these wandering comets pass through our solar system every year and this is just the first one we've seen come so close to the sun that we can see it. The prospect is exciting - it has a lot to teach us about the mixing of masses in the galaxy. If a hyperbolic comet can carry samples of Earth life away to a different star, then a hyperbolic comet can bring the life from another star here. For all we know Earth gets hit by one of these every 30 million years and passes through its coma quite more often. In terms of the age of the galaxy Earth is quite young, this cometary composition has been quite common for more than three times the age of our solar system, there is considerable mass exchange between stars.
If this one picks up life from here and carries it to another star who are we to say that life as we know it didn't arrive here this same way? We have actual, factual evidence of interstellar comets and the rest we know for fact too. Life began on Earth suspiciously soon for biogenesis to happen here. The Milky Way had an 8 billion years head start on us, and a vaster field for biogenesis to occur by about 20 billion times.
Intelligent life is a different question. Given our own experience it seems unlikely even here, and likely to be brief as well given our lack of interest in off-planet backups and the narrow window in which such a thing is possible. Soon the Holocene interglacial epoch will end and then it's back into the cold and dark for us as well - and with it our ability to save Man from what seems an inevitable collision with physics. If we fail to achieve interplanetary persistence it's likely Man will die out or at least lose his science culture sometime in the next 5,000 years - and that figure is extremely generous.
Panspermia theory just got a big bump. Fermi is still equal weight. If we navigate this danger then Fermi looms: why didn't others?