Scientists looking for life beyond Earth have a new target relatively close to home.
The dwarf planet Ceres, which orbits in the Main Asteroid Belt between Mars and Jupiter, has organic compounds on its surface, a paper published in this week's Science shows.
The discovery, made with NASA's orbiting Dawn spacecraft, follows earlier findings that the 590-mile wide Ceres may have an ocean beneath its frozen surface.
"There are speculations about a subsurface ocean on Ceres, similar to Europa or Enceladus," planetary scientist Michael Kuppers, with the European Space Astronomy Center in Madrid, told Seeker.
Europa, a moon of Jupiter, and Enceladus, a moon circling Saturn, are two prime targets in the search for life beyond Earth.
"I do think Ceres is a good target for searches for life outside Earth," Kuppers said. "In addition to distance, the radiation environment is more benign than, for example, Europa."
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Dawn lead scientist Christopher Russell, with the University of California Los Angeles, said the discovery means that Ceres should be further explored, but noted that these organic molecules "are a long way from microbial life."
"Ceres should be relatively easy to land on and has a benign environment compared to bodies further out in the solar system," Russell wrote in an email to Seeker. "We could take a small chemical lab to Ceres and analyze its soil and exosphere."
Data collected by Dawn's visible and near-infrared imaging spectrometer showed the organic material matches tar-like compounds such as kerite or asphalitite, lead researcher Maria Cristina De Sanctis, with the National Institute for Astrophysics in Rome, Italy, and colleagues write in the Science paper.
A follow-on analysis showed the organics are native to Ceres, most likely formed by hydrothermal activities beneath the surface.
"These compounds are unlikely to have been delivered from an exterior source in an impact... because the extreme heat from an impact would have destroyed these types of compounds," Science wrote in a summary of the research.
The location of the organics also casts doubt that they arrived via a crashing asteroid or comet.
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Scientists found the organics on two sites on Ceres, including on a crater rim.
"The simplest explanation is that they were produced inside Ceres," Russell said.
On a bigger picture, the discovery of organics on Ceres, which orbits nearly three times farther away from the sun than Earth, shows that the building blocks for life were present from the start of the solar system some 4.6 billion years ago.
"If we consider Ceres to be typical of the planetesimals forming about 3 million years after day one of the solar system, the discovery indicates that the starting material in the solar system contained the essential elements... for life," Russell said.
"Ceres may have been able to take this process only so far," he added. "Perhaps bodies in between Earth and Ceres in complexity, such as Europa and Mars, will enable us to fill in the gaps in our understanding of the beginning of life."
Caption: False color view of Ceres and its Occator Crater. Organics were found near another crater named Ernutet. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA WATCH VIDEO: What You Need To Know About Organic Matter On Ceres