Ceres is the only dwarf planet in the inner Solar System and it was visited by the Dawn mission last decade. NASA’s spacecraft revealed that the world hosts complex organics, possible volcanism where salt erupted, and plenty of water ice. The origin of organics was not fully understood: were they native to Ceres or were they brought by carbon-rich asteroids?
Ceres might have been a water world, with a subsurface ocean where interesting chemistry might have happened. So if the organics are native to Ceres, it might imply something very important about the dwarf planet's past habitability.
“The organics were initially detected in the vicinity of a large impact crater, which is what motivated us to look at how impacts affect these organics,” Terik Daly, a planetary scientist at the Johns Hopkins Applied Physics Laboratory who led this study, said in a statement. “We are finding that organics may be more widespread than first reported and that they seem to be resilient to impacts with Ceres-like conditions.”
Their approach was to reproduce in the lab the conditions of an impact on the surface of Ceres. The team used the NASA Ames Vertical Gun Range to shoot organics that match the profile of what has been seen on the dwarf planet. The impacts happened at speeds between 2 to 6 kilometers per second (4,400–13,000 miles per hour) and with angles varying between 15 and 90 degrees relative to horizontal.
The experimental data provided important insights, but it was not enough to answer the "origin" questions. The team combined two different data streams from NASA’s Dawn – its camera dataset and the spectroscopy – to have a more detailed map of the location of organics on the dwarf planet. Together, the research supports the idea that the organics came from inside Ceres.
“People had looked at the Dawn camera data and the Dawn spectrometer data separately, but no one else had taken the approach our team used to extrapolate the data from one instrument to another, which provided new leverage in our search to map and understand the origin of organics on Ceres,” explained co-author Jessica Sunshine, an astronomer at the University of Maryland.
“By capitalizing on the strengths of two different datasets collected over Ceres, we’ve been able to map potential organic-rich areas on Ceres at higher resolution. We can see a very good correlation of organics with units from older impacts and with other minerals like carbonates that also indicate the presence of water. While the origin of the organics remains poorly understood, we now have good evidence that they formed in Ceres and likely in the presence of water,” added Juan Rizos, an astrophysicist at the Instituto de Astrofisica de Andalucia in Spain.
“There is a possibility that a large interior reservoir of organics may be found inside Ceres. So, from my perspective, that result increases the astrobiological potential of Ceres.”
The research was presented Tuesday at the Geological Society of America’s GSA Connects 2023 meeting.