Researchers have discovered that the dwarf planet Ceres has a surprisingly high amount of organic matter sitting in spots on its icy rock surface.
Brown University astronomers have conducted a new study that looks into how much organic material is available on Ceres. Their analysis shows there is far more organics on the dwarf planet than early discoveries show.
The method employed could also open up new insight on how astronomers study extraterrestrial organic material.
"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," study lead Hannah Kaplan of Southwest Research Institute says.
Details of the study are published in the Geophysical Research Letters.
Finding Organic Molecules On Ceres
Astronomers first found organic material lurking in the Ernutet Crater region on Ceres' northern hemisphere in 2017.
Organic material is made of carbon-based compounds that are essential to life. All living things on Earth are made up of organic molecules. However, finding organics on Ceres does not mean that life exists or existed there. There are chemical reactions that can lead to carbon-based compounds without creating biological material.
Ceres is particularly intriguing for astronomers because it is also abundant in icy water. Water is also an element that is essential to life, at least to life as humans know it.
Using the Visible and Infrared instrument on NASA's Dawn orbiter, which flew into orbit in 2015, astronomers discovered the existence of organic molecules on Ceres.
By looking at which waves of light from the sun were reflected or absorbed by the surface of the planet, scientists were able to determine what compounds were present. Using this method, they were able to detect a wavelength that corresponds to organic molecules on the floor of Ernutet Crater.
To find out how much organic material was available, they plotted the reflectance of organic material on Earth and compared it with their findings on Ceres. The initial discovery was around 6 to 10 percent of the signal was organic matter.
The team at Brown University says there is much more than that.
New Method Of Studying Extraterrestrial Organics
Instead of using Earth rocks, the team from Brown used meteorites. Meteorites, which used to be part of asteroids that had broken off, contain carbonaceous chondrite. There is a significant amount of organic matter found on meteorites.
However, organic matter on meteorites have a different reflectance from Earth organics. The researchers believe it may be more appropriate to use organic matter from meteorites to compare with organic material found on Ceres.
"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 says.
They estimate that as much as 40 to 50 percent of the signal they are getting from Ceres could comprise organic matter.
Where Did The Organic Material Come From?
The researchers offer two hypotheses for the origin of organic material on the dwarf planet. One, it could have been made internally and then transported to the surface. The other hypothesis is it could have come from an impact with an organic-rich comet or asteroid.
If organic matter came to Ceres by impact, the researchers believe the object of impact would more likely be a comet since comets are more abundant in organics than asteroids. Heat made from such an impact, however, could have reduced the amount of organic material available.
If the organic matter was made internally, it raises the question of why the material is concentrated in the northern hemisphere.