Scientists have identified a new type of large, dark space rock in the main asteroid belt between Mars and Jupiter that is flush with water.
This asteroid group has striking similarities to Ceres, the only dwarf planet within the inner part of the solar system, known for being chock-full of H2O. But these asteroids — though relatively close to Ceres — are orbiting farther out in the belt than their much larger sibling.
The discovery, made with measurements taken at the NASA Infrared Telescope Facility in Hawaii, adds to the mounting evidence indicating asteroids in the main belt migrated there from a cold nether region, perhaps beyond the orbit of Neptune or Pluto. Such clues suggest the massive gravity of giant planets in the primitive solar system changed their travel plans, nudging the asteroids to their present location, relatively closer to the sun.
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How Earth got water
The new class of asteroids might thrill astronomers who are proponents of the theory that Earth's oceans formed from icy comets and asteroids smashing into the planet. While some scientists believe primitive Earth vented out gasses 4.5 billion years ago, eventually creating an atmosphere that allowed rain to fall and pool, many believe the large bodies of water formed because space rocks from the outer edge of the solar system brought water to it or some combination of the two. The mystery hasn't been solved yet.
Though this group of asteroids isn't quite a "missing link" to Earth's hydration history, the research does back up the idea that super faraway rocks brought ingredients for water to an otherwise arid region of the solar system, said Andy Rivkin, a planetary astronomer at Johns Hopkins University's Applied Physics Lab. Rivkin, who wasn't involved in this study, is an expert on asteroids with water and organic materials.
"This would be perhaps the kind of objects that made it into the solar system and brought ice and organics with them," Rivkin told Mashable. "Their cousins might have hit the Earth and brought some of that, as well as hitting Mars."
Millions of asteroids orbit the sun. They're the rubble left over from the formation of the solar system about 4.6 billion years ago. Often asteroids get stereotyped as menaces of the planetary neighborhood, snatching sensational headlines for coming "close to Earth," even when they're safely tumbling millions of miles off in the distance. Astronomers tend to think of them as menial rocks that couldn't quite hack it, never coalescing and amounting to an actual planet.
But their scientific value is undeniable, providing an ancient record of the complex chemical and physical changes that happened over time in the solar nebula — the gas and dust cloud from which the sun and planets formed, said Driss Takir, lead author of the study published in Nature Astronomy this week. The new Ceres-like class of asteroids, rich in water and carbon, possess the same ingredients essential to life on Earth.
"These asteroids can help us better understand the origin and evolution of our solar system," he told Mashable.
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"These asteroids can help us better understand the origin and evolution of our solar system."
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Scientists from Heidelberg University in Germany who collaborated on the research used computer simulations to study how these asteroids could have migrated from the outer solar system to today's asteroid belt.
After observing 100 carbonaceous asteroids with infrared spectroscopy, a process of measuring the light reflected from a surface to reveal information about its minerals, Takir has detected 15 dark and water-rich asteroids like Ceres. With more observations, he believes scientists will be able to estimate just how many others like them exist in the main asteroid belt.
What Ceres is made of
As cosmic objects go, Ceres was pretty obscure before 2006, known to experts then as a huge, 500-mile-wide asteroid more than 250 million miles from the sun. At the same time the scientific community demoted Pluto from planet to dwarf planet, Ceres was being upgraded to dwarf planet. Then, in 2015, a NASA spacecraft got a closer look at the unusual bright patches visible on Ceres' surface.
Through the Dawn mission, scientists learned that Ceres was an ocean world. Its white spots were a salty crust of sodium carbonate, the same type of salt people use as a water softener. After looking at the mission data, scientists concluded that the salt was the residue of a vast, briny reservoir about 25 miles underground and hundreds of miles wide. Meteorite impacts either melted slush just below the surface or created large fractures in the dwarf planet, allowing salt water to ooze out of ice volcanoes.
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Astrobiologists are interested in whether primitive lifeforms could exist on Ceres, the closest ocean world to Earth. The National Academies Planetary Science Decadal Survey recently recommended that NASA send a robotic spacecraft to land on Ceres to collect samples.
Just like Ceres, the discovered asteroids have minerals on their surfaces that derive from an interaction with liquid water. The research suggests at least some of these asteroids may also have water ice.
"Especially asteroid 10 Hygiea, the largest dark Ceres-like asteroid with a near-spherical shape," Takir said. "We will need high-resolution spacecraft observations to search for water ice on these asteroids."
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Despite the strong case for outer solar system objects bringing water ingredients inward, the research team didn't find any meteorite material on Earth matching the new class of asteroids. That wouldn't seem to bode well for the theory if those objects never make the long journey to Earth.
But scientists say just because you don't find pieces of them on the ground, doesn't mean they're not here.
"If you throw a snowball at Earth, it's going to not really make it through the atmosphere because it'll kind of heat up and melt and vaporize," Rivkin said. "But the water would be added to the atmosphere."
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