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Watery asteroids hint at possibility of extraterrestrial life

October 14, 2013 6:02pm
Scientists may soon turn to water-rich asteroids to see if life once existed in a dead solar system—or if the star system can potentially support life as we know it, outside of Earth.
 
Lucyna Kedziora-Chudczer of the University of New South Wales said this could help us in the future, when our own Sun evolves into a hot white dwarf and engulfs the Earth.
 
"Information about the distribution and abundance of water-enriched planets can help us search for habitable worlds outside our own solar system," she said in an article published on ScienceAlert.
 
Chudczer said the Sun will run out of fuel in the distant future, and become a white dward after billions of years.
 
But before that, it will become a red giant, consuming the Earth and the inner planets, and leaving behind only the giant planets and their moons.
 
"If our star is merciful in this monstrous phase, then the asteroid belt might just survive as well. No guarantees," she said.
 
Water vapor
 
Presently, she said only a few planets outside our solar syste, have solid signs of water vapor in their spectra.
 
Yet, she said most of them like HD189733b are “hot Jupiters” where she said "life as we know it cannot exist."
 
However, one promising planet in terms of possible habitability is GJ 1214b, discovered during the MEarth search for extra solar planets.
 
"It is only a few times heavier than the Earth. Its low density suggests it’s watery, with only 25% of its mass as rocky material. Observations of its almost featureless optical and infrared spectrum also suggest that GJ 1214b could possibly be a water-dominated world," she added.
 
However, she said the composition of the planet is still debated, with models suggesting it could be a rocky planet with an extensive hydrogen-rich atmosphere.
 
White dwarf GD61
 
Chudczer said a team led by astronomer Jay Farihi is now studying planetary debris around the white dwarf GD61.
 
"In a CSI-style forensic deduction, Farihi’s team sifted through the last meal consumed by GD 61. And they found that some of that excess oxygen must have been locked into water molecules within the swallowed debris," she said.
 
Yet, she said the only way water could survive around the white dwarf is if it were buried within a large asteroid-type object.
 
And the asteroid would have to be about the same mass as Vesta, one of the largest asteroids in our solar system.
 
Chudczer also noted there is one similarly water-rich massive object in our solar system, the dwarf planet Ceres, which is 20 percent water ice.
 
Water delivery
 
On the other hand, Chudczer said water from asteroids, like those swallowed by GD 61, may have played a major role in the evolution of life on our own Earth.
 
Presently, she said the origin of water on Earth is still unclear.
 
"The Earth formed in the much hotter region of the inner solar system so it must have been rather dry in comparison. Clearly the Earth’s water abundance by mass is much lower than that of objects in the outer solar system, but even this low amount of water could not have formed in the planet’s current location," she said.
 
This could support some theories suggesting Earth’s oceanic water came from somewhere else - like the outer regions of the solar system, delivered by meteorites or comets hitting Earth in its early stages.
 
"If the final stages of our solar system are anything like the GD 61 system, finding a substantial amount of material enriched in water in the debris surrounding stellar remnants should perhaps not be so surprising. Only such debris, originally formed on the outskirts of a stellar system far from the blazing heat of its parent star, have a chance of surviving the late stages of stellar evolution," she said.
 
However, she also said systems like GD 61 that show an overabundance of oxygen do not appear to be common.
 
"This is testimony to the rich diversity of continually discovered exo-planetary systems that are nothing like our own solar system," she said. — TJD, GMA News



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