By: Clara Moskowitz
Published: 09/20/2012 02:46 PM EDT on SPACE.com
The protoplanet Vesta, a large space rock in the solar system's asteroid belt, is covered with a surprising amount of hydrogen, and bits of Vesta may have rained down on Earth in the form of meteorites, NASA's Dawn probe has revealed.
Dawn spent more than a year orbiting Vesta, a behemoth 330-mile-wide (530 kilometers) asteroid that circles the sun between the orbits of Mars and Jupiter. Earlier this month, on Sept. 5, Dawn took its leave of Vesta to begin trekking to the even-larger space rock Ceres, which is categorized as a dwarf planet.
Meanwhile, though, scientists are still poring over the treasure trove of data on Vesta gathered by the probe, and two new studies are reported today (Sept. 20) in the journal Science. In one, researchers report the findings of Dawn's Gamma Ray and Neutron Detector (GRAND), which mapped the elemental composition of Vesta's surface.
"We were surprised to see that Vesta has a significant amount of hydrogen," said Thomas Prettyman of the Planetary Science Institute in Tucson, Ariz., leader of one of the new studies. [Photos: Asteroid Vesta and NASA's Dawn Spacecraft]
A perspective view of Marcia crater, Vesta. Marcia (70 km in diameter) is one of the youngest large craters on Vesta and host to the largest concentration of pits on the asteroid. Image released September 20, 2012.
Bits of Vesta on Earth
GRAND showed a widespread abundance of the element hydrogen, which was not thought to be prevalent on Vesta. Furthermore, Vesta's composition appears strikingly similar to a class of meteorites on Earth called howardite, eucrite and diogenite (HED), leading scientists to think these chunks of rock originally came from Vesta.
"This firmly links the HED meteorites to Vesta," Prettyman told SPACE.com. "The significance and importance of that is if you know these meteorites come from Vesta, you can study them in great detail in a lab and learn about how Vesta formed. Vesta is a frozen planetary embryo, frozen at a very early stage of development."
Scientists think Vesta was created within the first few million years of the solar system's existence, and could have turned into a full-fledged planet, had things worked out differently. By studying this failed planet, researchers could learn more about how Earth came to be.
"Vesta is the second most massive asteroid in our solar system and provides the opportunity to study the early Earth as a developing planet while it was still barely one-sixth the size of the moon," MIT scientist Richard Binzel, who was not involved in the research, wrote in an accompanying essay in Science.
A second paper in Science reports "unusual pitted terrain" on Vesta characterized by strange rimless depressions on the asteroid's surface in and near impact craters.
Similar landscapes have been seen on Mars, where the indentations are thought to form when chemicals vaporize off the surface after being heated by impacting space rocks, wrote the scientists, led by Brett Denevi of the Johns Hopkins Applied Physics Laboratory.
This finding ties in with the revelation of hydrogen on Vesta, because the likeliest explanation for the indentations on the surface is that hydrogen, which is likely bound up in minerals there, is released in the form of water vapor when the material is heated up by impacts.
Ultimately, the new studies offer some surprises, and some confirmations of the coalescing picture scientists have about this early stage of the solar system's history. These findings would not have been possible without the up-close study of this world provided by Dawn, the researchers said.
The probe entered a special low-altitude orbit for about five months to allow the GRAND instrument to analyze emissions from Vesta's surface that result from collisions between cosmic ray particles and elements in the asteroid's dirt.
"Dawn's crowning success at Vesta was the delivery of instruments that require proximity, exemplified by the gamma-ray and neutron measurements of Prettyman et al. yielding elemental abundances that unequivocally confirm the meteorite links," Binzel wrote.
The $466 million Dawn spacecraft launched in September 2007 and arrived at Vesta in July 2011. It is due to arrive at Ceres in February 2015.
- The 7 Strangest Asteroids in the Solar System
- Hydrogen Found On Asteroid Vesta In Abundance | Video
- How NASA's Dawn Asteroid Mission Works (Infographic)
Also on HuffPost:
Dawn Orbiting Vesta
This artist's concept shows NASA's Dawn spacecraft orbiting the giant asteroid Vesta. The depiction of Vesta is based on images obtained by Dawn's framing cameras. Image: NASA/JPL-Caltech/JAXA/ESA
Different Shades of Vesta
NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. Scientists are studying image like these to better understand the different materials on the surface. Image: NASA/JPL-Caltech/JAXA/ESA
Perspective View of Layered Young Crater
This image, made from data obtained by NASA's Dawn spacecraft, shows a perspective view of a layered young crater in the Rheasilvia basin at Vesta. (It is the same crater as Fig. 3.) It was created from laying images from the mission's low-altitude mapping orbit (an average of 130 miles or 210 kilometers above the surface) atop a digital terrain model. Image: NASA/JPL-Caltech/JAXA/ESA
Visible and Infrared Mapping Spectrometer False-Color Image
These images were obtained by the Dawn spacecraft on July 23, 2011. The bottom two images are false-color, where different colors represent visible and infrared light wavelengths. Image: NASA/JPL-Caltech/JAXA/ESA
Full-Frame Image of Vesta
NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers). Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body. After that, the next stop on its itinerary will be an encounter with the dwarf planet Ceres. Image: NASA/JPL-Caltech/JAXA/ESA
A False-Color Topography of Vesta's South Pole
This false-color map of the giant asteroid Vesta was created from stereo images obtained by the framing camera aboard NASA's Dawn spacecraft. The image shows the elevation of surface structures with a horizontal resolution of about 750 meters per pixel. Image: NASA/JPL-Caltech/JAXA/ESA
Vesta Sizes Up
This composite image shows the comparative sizes of nine asteroids. Up until now, Lutetia, with a diameter of 81 miles (130 kilometers), was the largest asteroid visited by a spacecraft, which occurred during a flyby. Image: NASA/JPL-Caltech/JAXA/ESA
Crater in Shadow on Vesta
This image, one of the first obtained by NASA's Dawn spacecraft in its low altitude mapping orbit, shows part of the rim of a fresh crater on the giant asteroid Vesta. The terrain shown here is located in an area known as the Heavily Cratered Terrain in the northern hemisphere. Image: NASA/JPL-Caltech/JAXA/ESA
Viewing the South Pole of Vesta
This image obtained by the framing camera on NASA's Dawn spacecraft shows the south pole of the giant asteroid Vesta. Image: NASA/JPL-Caltech/JAXA/ESA