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ORGANIC MOLECULES

Ceres, the building blocks for life

Organics on Ceres may be more abundant than originally thought. The new study on Geophysical Research Letters

Last year, scientists with NASA's Dawn mission announced the detection of organic material exposed in patches on the surface of the dwarf planet Ceres.

 

Now, a new analysis of the Dawn data by Brown University researchers suggests those patches may contain a much higher abundance of organics than originally thought.

 

The findings, published recently in Geophysical Research Letters, raise intriguing questions about how those organics got to the surface of Ceres, and the methods used in the new study could also provide a template for interpreting data for future missions, the researchers say.

 

“What this paper shows is that you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data – said Hannah Kaplan, a postdoctoral researcher at the Southwest Research Institute who led the research while completing her Ph.D. at Brown – That's important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material.”

 

The original discovery of organics on Ceres was made using the Visible and Infrared (VIR) Spectrometer provided by the Italian Space Agency. By analyzing the patterns in which sunlight interacts with the surface -- looking carefully at which wavelengths are reflected and which are absorbed -- scientists can get an idea of what compounds are present on Ceres. The VIR instrument picked up a signal consistent with organic molecules in the region of Ernutet Crater on Ceres' northern hemisphere.

 

To get an initial idea of how abundant those compounds might be, the original research team compared the VIR data from Ceres with laboratory reflectance spectra of organic material formed on Earth. Based on that standard, the researchers concluded that between six and 10 percent of the spectral signature they detected on Ceres could be explained by organic matter.

 

But for this new research, Kaplan and her colleagues wanted to re-examine those data using a different standard. Instead of relying on Earth rocks to interpret the data, the team turned to an extraterrestrial source: meteorites. Some meteorites have been shown to contain organic material that's slightly different from what's commonly found on our own planet. And Kaplan's work shows that the spectral reflectance of the extraterrestrial organics is distinct from that of terrestrial counterparts.

 

“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there," Kaplan said. "We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That's a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”