What if an asteroid caromed off the Earth billions of years ago and continued its journey? What if that same asteroid and/or its impact debris came into contact with more planets, worlds where the Earth's DNA might also flourish?
Scientists are attempting to locate stars from our own Sun's original star cluster in the hope of discovering life outside the Solar System. Working on the theory that the Earth itself could have seeded life on other worlds billions of years ago, the search is on to find siblings of the Sun.
"The idea is if a planet has life, like Earth, and if you hit it with an asteroid, it will create debris, some of which will escape into space," astronomer Mauri Valtonen of Finland's University of Turku explained to Space.com. "And if the debris is big enough, like 1 meter across, it can shield life inside from radiation, and that life can survive inside for millions of years until that debris lands somewhere. If it happens to land on a planet with suitable conditions, life can start there."
Scientists believe that if such a "seeding" ever occurred involving Earth, it most likely happened while the Sun was still in its formative star cluster about 3.5 billion years ago. (The Earth is estimated to be just slightly younger than the Sun, which is 4.5 billion years old.) An asteroid or planetoid crashing into the Earth during this time -- which is believed to have been one of constant collision between celestial bodies -- would have produced optimal circumstances for Earth microorganisms to be transferred to another star -- and another world.
The research, of course, also suggests that the same could be true of the Earth -- that life on Sol's third world was seeded by just such a transferral of microbial organisms.
Valtonen presented his findings at the 219th meeting of the American Astronomical Society. By studying the radial velocities of stars in the HIPPARCOS catalog, the astronomer and his fellow researchers found two prime candidate stars that most resembled the Sun in evolutionary stage and metal content, HIP 87382 and HIP 47399. The stars are both about 100 light years away and just might have been born in the same star cluster as the Sun.
Valtonen and his colleagues now plan to study the candidate stars to attempt to detect planetary systems.
The astronomer told Space.com, "If we find an Earth-type planet, then it'd be a nice target for this new generation of detectors to point at the atmosphere of the planet. If there's a planet and it has signs of life, then we could say perhaps they are relatives in some sense."
The new generation of detectors include both ground- and space-based telescopes, such as NASA's Kepler and a number of large array telescopes. These include those capable of studying other worlds through atmospheric spectral analysis. Such analyzation helps detect and determine the chemical properties of faraway atmospheres. Certain signatures could be indicative that some form of life exists on these extrasolar planets.
Valtonen's search for conditions for extraterrestrial life is just another avenue where scientists hope to find life elsewhere in the universe.
Most searches for Earth-like life currently center around stars' "habitable zones," an area around a parent star where liquid water can form and where the conditions would be "just right" to sustain life (as it is recognized by our science). Most extrasolar planets discovered thus far have been gas giants and "super-Earths," planets that hold out the possibility of being Earth-like except for their relative masses.
But there are those who believe that the parameters should be stretched to include the possibility that biological entities might exist that do not conform to human standards and conditions. Researchers at MIT detailed findings last year that suggested that it was possible to extraterrestrial life could evolve to breathe in a sulfurous atmosphere. And researchers from NASA and Tokyo University reported in Astrobiology Magazine that life might be more likely found on planets that actually have more land than water -- like the fictitious world of Frank Herbert's Arrakis in Dune -- and that the habitable zone around stars increased by three times for such candidate planets.
Shawn Domagal-Goldman, an astrobiology specialist and researcher at NASA headquarters in Washington, predicted earlier this month that scientists would find an Earth "twin" before the end of 2014. The astrobiologist noted that such a "Goldilocks planet" might support life.
The possibility exists that such a planet could be found around one of the stars Valtonen believes might be a sibling to the Sun.
(photo credit: NASA, Wikimedia Commons)
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