When reflecting on the so-called (according to NASA) reflections of light inside the Occator crater on the surface of the dwarf planet Ceres, it’s a good idea not to get too attached to the explanation. Researchers analyzing data not from the Dawn spacecraft but from a planet-hunting telescope say the lights are brightening and dimming at random times throughout the day for no apparent reasons. Is it again time to suspect aliens?
While Dawn sent back stunning photos from its approach to and orbit of Ceres, there are other ways to watch it. Astronomers from the INAF-Trieste Astronomical Observatory in Trieste, Italy, used the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at the European Southern Observatory (ESO) in Chile to observe Ceres for two nights in July 2015 and August 2015. Specifically, they watch the rotation of Ceres as is spins once every nine hours.
The result was a surprise. We did find the expected changes to the spectrum from the rotation of Ceres, but with considerable other variations from night to night.
Antonino Lanza, co-author of the report in the journal Monthly Notices of the Royal Astronomical Society, says they expected to see the reflections change due to the rotation in Ceres' position relative to the Sun, but the random changes in brightness may indicate that the material causing the lights is not hydrated magnesium sulfates (Epsom salts) , as NASA said in its latest reports on the Dawn photos, but something volatile that is affected by the heat of the Sun.
The spots were also observed to move faster than predicted based on the velocity of Ceres rotation. Combined with the random changes in brightness, the astronomers speculate that the the lights are caused by reflections off of not solid hydrated magnesium sulfates but plumes of gas released by the evaporation of some frozen material pushed to the surface by activity beneath it. That activity could be volcanoes, geysers, water flow or something yet to be determined.
Meanwhile, Dawn is still in orbit and still sending back pictures, which NASA will now compare to the analysis of the Harp astronomers, says Chris Russell, Dawn's principal investigator at UCLA.
We are now comparing the spots with the reflective properties of salt, but we are still puzzled by their source. We look forward to new, higher-resolution data from the mission's next orbital phase.
Controversy and competition on the cause of the curiosities in the crater of Ceres. No aliens but still fun and interesting.