Asteroid Ice May Be Living Fossil With Clues To Oceans' Origins

The first-ever discovery of ice and organic molecules on an asteroid may hold clues to the origins of Earth's oceans and life 4 billion years ago.

University of Central Florida researchers detected a thin layer of water ice and organic molecules on the surface of 24 Themis, the largest in a family of asteroids orbiting between Mars and Jupiter.

Their unexpected findings will be published in Nature, which will featuretwo complementary articles by the UCF-led team and by another team of planetary scientists.

"What we've found suggests that an asteroid like this one may have hit Earth and brought our planet its water," said UCF Physics Professor HumbertoCampins, the study's lead author.

Some theories suggest asteroids brought water to Earth after the planet formed dry. Scientists say the salts and water that have been found in some meteorites support this view.

Using NASA's Infrared Telescope Facility in Hawaii, Campins and his team of researchers measured the intensity of the reflected sunlight as 24 Themis rotated. Differences in intensity at different wavelengths helped researchers determine the makeup of the asteroid's surface.

Researchers were surprised to find ice and carbon-based compounds evenly distributed on 24 Themis. More specifically, the discovery of ice is unexpected because surface ice should be short lived on asteroids, which are expected to be too warm for ice to survive for long.

The distance between this asteroid and the sun is about three times greater than between Earth and the sun.

Researchers will continue testing various hypotheses to explain the presence of ice. Perhaps most promising is the possibility that 24 Themis might have preserved the ice in its subsoil, just below the surface, as a kind of "living fossil" or remnant of an early solar system that was generally considered to have disappeared long ago.

Scientists Finds Evidence Of Water Ice On Asteroid's Surface

This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid's surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville

Asteroids may not be the dark, dry, lifeless chunks of rock scientists have long thought.

Josh Emery, research assistant professor with the earth and planetary sciences department at the University of Tennessee, Knoxville, has found evidence of water ice and organic material on the asteroid 24 Themis. This evidence supports the idea that asteroids could be responsible for bringing water and organic material to Earth.

The findings are detailed in the journal "Nature."

Using NASA's Infrared Telescope Facility on Hawaii's Mauna Kea, Emery and Andrew Rivkin of Johns Hopkins University in Laurel, Md., examined the surface of 24 Themis, a 200-kilometer wide asteroid that sits halfway between Mars and Jupiter.

By measuring the spectrum of infrared sunlight reflected by the object, the researchers found the spectrum consistent with frozen water and determined that 24 Themis is coated with a thin film of ice. They also detected organic material.

"The organics we detected appear to be complex, long-chained molecules. Raining down on a barren Earth in meteorites, these could have given a big kick-start to the development of life," Emery said.

Emery noted that finding ice on the surface of 24 Themis was a surprise because the surface is too warm for ice to stick around for a long time.

"This implies that ice is quite abundant in the interior of 24 Themis and perhaps many other asteroids. This ice on asteroids may be the answer to the puzzle of where Earth's water came from," he said.

Still, how the water ice got there is unclear.

24 Themis' proximity to the sun causes ice to vaporize. However, the researchers' findings suggest the asteroid's lifetime of ice ranges from thousands to millions of years depending on the latitude.

Therefore, the ice is regularly being replenished. The scientists theorize this is done by a process of "outgassing" in which ice buried within the asteroid escapes slowly as vapor migrates through cracks to the surface or as vapor escapes quickly and sporadically when 24 Themis is hit by space debris.

Since Themis is part of an asteroid "family" that was formed from a large impact and the subsequent fragmentation of a larger body long ago, this scenario means the parent body also had ice and has deep implications for how our solar system formed.

The discovery of abundant ice on 24 Themis demonstrates that water is much more common in the Main Belt of asteroids than previously thought.

"Asteroids have generally been viewed as being very dry. It now appears that when the asteroids and planets were first forming in the very early Solar System, ice extended far into the Main Belt region," Emery said.

"Extending this refined view to planetary systems around other stars, the building blocks of life - water and organics - may be more common near each star's habitable zone. The coming years will be truly exciting as astronomers search to discover whether these building blocks of life have worked their magic there as well."

The scientists' discovery also further blurs the line between comets and asteroids. Asteroids have long been considered to be rocky and comets icy. Furthermore, it was once believed that comets could have brought water to Earth. This theory was nixed when it was discovered comets' water has different isotopic signatures than water on Earth.

Now, due to Emery and Rivkin's findings, many wonder if asteroids could be responsible for seeding Earth with the ingredients for life.

The Mystery Of Moonwater

Mini-SAR map of the Circular Polarization Ratio (CPR) of the north pole of the Moon. Fresh, “normal” craters (red circles) show high values of CPR inside and outside their rims. This is consistent with the distribution of rocks and ejected blocks around fresh impact features, indicating that the high CPR here is surface scattering. The “anomalous” craters (green circles) have high CPR within, but not outside their rims. Their interiors are also in permanent sun shadow. These relations are consistent with the high CPR in this case being caused by water ice, which is only stable in the polar dark cold traps. We estimate over 600 million cubic meters (1 cubic meter = 1 metric ton) of water in these features.

Main L, 14 km diameter, 81.4° N, 22° E

View a Larger version of the fresh crater CPR (537KB).

The fresh impact crater Main L (14 km diameter), which shows high CPR inside and outside its rim. SC is the “same sense, circular” polarization; CPR is “circular polarization ratio.” The histograms at right show that the high CPR values within (red line) and outside the crater rim (green line) are nearly identical.
Anomalous Polar Crater

On Floor of Rozhdestvensky, 9 km Diameter, 84.3° N, 157° W

View a Larger version of the Anomalous Polar Crater (627KB).

An “anomalous” crater on the floor of Rozhdestvensky, near the north pole of the Moon. This feature shows high CPR within the crater rim, but low CPR outside, suggesting that roughness (which occurs throughout a fresh crater) is not the cause of the elevated CPR. This feature’s interior is in permanent sun shadow. SC stands for “same sense, circular”, OC stands for “opposite sense, circular” and CPR is the “circular polarization ratio.” The histogram of CPR values clearly shows that interior points (red line) have higher CPR values than those outside the crater rim (green line).
Moonwater. Look it up. You won't find it. It's not in the dictionary. That's because we thought, until recently, that the Moon was just about the driest place in the solar system. Then reports of moonwater started "pouring" in - starting with estimates of scant amounts on the lunar surface, then gallons in a single crater, and now 600 million metric tons distributed among 40 craters near the lunar north pole."We thought we understood the Moon, but we don't," says Paul Spudis of the Lunar and Planetary Institute. "It's clear now that water exists up there in a variety of concentrations and geologic settings. And who'd have thought that today we'd be pondering the Moon's hydrosphere?"
Spudis is principal investigator of NASA's Mini-SAR team - the group with the latest and greatest moonwater "strike." Their instrument, a radar probe on India's Chandrayaan-1, found 40 craters each containing water ice at least 2 meters deep.
"If you converted those craters' water into rocket fuel, you'd have enough fuel to launch the equivalent of one space shuttle per day for more than 2000 years. But our observations are just a part of an even more tantalizing story about what's going on up on the Moon."
It's the story of a lunar water cycle, and it's based on the seemingly disparate - but perhaps connectable - results from Mini-SAR and NASA's recent LCROSS mission and Moon Mineralogy Mapper (M3 or "M-cubed") instrument also on Chandrayaan-1.
"So far we've found three types of moonwater," says Spudis. "We have Mini-SAR's thick lenses of nearly pure crater ice, LCROSS's fluffy mix of ice crystals and dirt, and M-cube's thin layer that comes and goes all across the surface of the Moon."
On October 9, 2009, LCROSS, short for Lunar Crater Observation and Sensing Satellite, struck water in a cold, permanently dark crater at the lunar south pole. Since then, the science team has been thoroughly mining their data.
"It looks as though at least two different layers of our crater soil contain water, and they represent two different time epochs," explains Anthony Colaprete, LCROSS principal investigator. "The first layer, ejected in the first 2 seconds from the crater after impact, contains water and hydroxyl bound up in the minerals, and even tiny pieces of pure ice mixed in. This layer is a thin film and may be relatively 'fresh,' perhaps recently replenished."
According to Colaprete, this brand of moonwater resembles the moonwater M3 discovered last year in scant but widespread amounts, bound to the rocks and dust in the very top millimeters of lunar soil.
The second layer is different. "It contains even more water ice plus a treasure chest of other compounds we weren't even looking for," he says. "So far the tally includes sulfur dioxide (SO2), methanol (CH3OH), and the curious organic molecule diacetylene (H2C4). This layer seems to extend below at least 0.5 meters and is probably older than the ice we're finding on the surface."
They don't know why some craters contain loads of pure ice while others are dominated by an ice-soil mixture. It's probably a sign that the moonwater comes from more than one source.
"Some of the water may be made right there on the Moon," says Spudis. "Protons in the solar wind can make small amounts of water continuously on the lunar surface by interacting with metal oxides in the rocks. But some of the water is probably deposited on the Moon from other places in the solar system."
The Moon is constantly bombarded by impactors that add to the lunar water budget. Asteroids contain hydrated minerals, and comet cores are nearly pure ice.
The researchers also think that much of the crater water migrates to the poles from the Moon's warmer, lower latitudes. "All our findings are telling us there's an active water cycle on the Moon," marvels Colaprete.
Think about it. The "driest place in the solar system" has a water cycle.
"It's a different world up there," says Spudis, "and we've barely scratched the surface. Who knows what discoveries lie ahead?"
Source:- NASA Science News

Large Amount of Water Found at Lunar North Pole

A recent investigation into datasets collected by a small NASA radar instrument revealed that existence of more than 40 craters at the north pole of the Moon that could be holding water-ice. The finding is of epic proportions, especially when considering that the LCROSS impactor made similar discoveries for water-ice at the south pole region. Additionally, other data collected from various spacecrafts proved the existence of significant amounts of water particles in other areas of the lunar surface as well. According to early results, it could be that more than 600 million metric tons of water ice exist at the lunar north pole, Space Fellowship reports.

The new data was collected by the NASA Mini-SAR instrument, which was mounted aboard the Indian space agency's (ISRO) Chandrayaan-1 spacecraft. The lightweight, synthetic aperture apparatus found roughly 40 small craters containing the stuff. The discovery is of significant importance, given the fact that future missions to the Moon would undoubtedly need to be able to procure their drinking water on-site. Carrying tons of water from Earth would be too expensive, and completely unpractical. The ice could also be used to produce oxygen for life support systems, as well as hydrogen for rocket fuel, that astronauts would use to return home.

“The emerging picture from the multiple measurements and resulting data of the instruments on lunar missions indicates that water creation, migration, deposition and retention are occurring on the Moon. The new discoveries show the moon is an even more interesting and attractive scientific, exploration and operational destination than people had previously thought,” says the Mini-SAR experiment principal investigator, Paul Spudis. He is an expert at the Houston, Texas-based Lunar and Planetary Institute. He adds that the craters found by the Mini-SAR instrument are between 2 and 15 kilometers (1 to 9 miles) in diameter.

“After analyzing the data, our science team determined a strong indication of water ice, a finding which will give future missions a new target to further explore and exploit,” adds Mini-RF Program program executive Jason Crusan, from the NASA Space Operations Mission Directoratem in Washington, DC. Full details of the discoveries made using the small synthetic-aperture radar are published in the latest issue of the respected scientific journal Geophysical Research Letters.

Finding Water Beyond the Solar System

Last year ended in a frenzy of amazing discoveries in our solar system. The LCROSS probe found definite evidence of water on the Moon, Cassini showed that Enceladus had a high probability of holding a liquid ocean under its icy surface, and Mars was proven again to have harbored an ocean in its earliest day. While these results are absolutely remarkable in themselves, some are not entirely satisfied with them, and want to push things even further. These people are scientists who are currently investigating methods of discovering water beyond the solar system, on exoplanets, Space reports.

One possible method of making this type of studies a reality is infrared spectroscopy. The method can be used to screen the protoplanetary discs around stars, or the dust that remained following their birth. If these areas contain hydrous minerals called phyllosilicates, then this could be a clear indicator of the presence of water. Naturally, we are not talking about liquid water, or even ice particles, but of trace amounts of the stuff, which make up a large portion of these minerals. Using IR spectroscopy in this manner is described in apaper published in a recent issue of the scientific journal Astrobiology.

“If you find phyllosilicates, you have most likely found liquid water. The objective was to try to determine whether we could actually detect these wonderful signatures of hydrated minerals almost always produced by the interaction of liquid water with rock,” Missouri State University Department of Physics, Astronomy and Materials Science visiting Professor Melissa Morris explains. The expert, who is also the author of the recent paper, is a research affiliate at the Arizona State University (ASU) School of Earth and Space Exploration.

What's very interesting about this approach is that, by studying a young star's protoplanetary disc, researchers could be able to determine what type of planet would eventually form around that particular celestial object. If the disc contains no traces of water, then a rocky, barren world will most definitely form. “I'm a huge advocate for looking for water in our own solar system, but just to understand the process of planetary system formation, we need to go outside our solar system and look at other systems as well,” Morris adds. The investigator is currently peering through data from the NASA Spitzer Space Telescope, an infrared observatory, in order to apply the new knowledge to real scenarios.