Ceres could be home to an ancient frozen ocean: a fascinating discovery just a few steps away
The dwarf planet Ceres seen by Dawn. The light areas are salt deposits at the bottom of craters. © NASA / JPL
The Solar System is full of watery worlds with oceans: Earth, of course, but also Europa, Enceladus, Dione, Mimas and Ceres. Until now, it was thought that the largest asteroid in the eponymous belt harbored an ocean hidden under a thick rocky surface. A study based on craters and based on data from the Dawn mission shows that this object could have a much more hydrated crust than previously thought.
Comparison of the Earth, the Moon and Ceres. With 950 km in diameter, it is approximately the size of France. © CWitte (public domain)
Ancient model of Ceres with a thick rocky crust and an underground ocean. © NASA / ESA
Relax, craters!
Published in the prestigious magazine Nature Astronomy, the study establishes that the surface of Ceres could contain 90% water and the rest in impurities. Until then, the weak relaxation of the craters (understand, their large number observable on the surface of Ceres) seemed to indicate that the crust contained no more than 30% water, the rest in rock.
Three scenarios were studied by the team: a) is that of an almost entirely rocky crust; b) a two-layer crust with the first more slippery than the second; c) with a very hydrated crust and gradually more rock. © Pamerleau, Sori & Scully (Nature Astronomy)
Computer simulation of the relaxation of a 12 km crater with vertical displacement in a crust made up of 90% frozen water. © Pamerleau, Sori & Scully (Nature Astronomy)
Their model establishes that an ancient muddy ocean, now completely frozen, perfectly explains why we still observe so many craters on Ceres. The water layer would actually be mixed with more and more rock up to around 117 km depth. This world would therefore resemble the moons Europa or Enceladus more – snowballs with an ocean under their icy crust – than our natural satellite, contrary to appearances.
Jupiter's moon Europa with its frozen water crust and its line pink. © Galileo (Nasa / JPL)
The small moon Enceladus around Saturn. © Cassini (Nasa / JPL)
And Ceres is not far from Earth!
Ceres' orbit is between those of Mars and Jupiter. © Orionist (public domain)
The missions Juice of the ESA, on the way to Europe, or Europa Clipper from NASA, will take years to reach their destination in order to study these aqueous worlds, where the hope of “alien” microbial life is real. What if a natural laboratory of extraterrestrial life orbited there, three times closer to us than the icy moons of Jupiter?
