Ceres has turned out to be an interesting challenge for planetary scientists. The dwarf planet has been studied for almost two years by NASA’s Dawn spacecraft, and while we have found some answers, we have also found many questions.
Among them, there’s the curious case of Ahuna Mons, Ceres’ ice volcano. You see, it’s not just one of several ice or cryovolcanoes on Ceres – it’s the only one. But a new paper published in Geophysical Research Letters is set to challenge that.
“Imagine if there was just one volcano on all of Earth. That would be puzzling,” pointed out lead author Michael Sori, of the Lunar and Planetary Laboratory at the University of Arizona, in a statement. “We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed.”
The team suspects that once these ice volcanoes had formed, they would start “melting” back into the planet. This doesn't happen on Earth because our volcanoes are made of rock, but the one on Ceres contains ice, which makes it possible. This phenomenon is called viscous relaxation and would cause the solid ice to flatten out over hundreds of millions of years.
To test this hypothesis, the researchers looked at how long it would take Ahuna Mons to deform. Ahuna Mons is 4 kilometers (2.5 miles) tall, and with Ceres' diameter being just 950 kilometers (590 miles), it is actually an impressively tall feature.
The researchers ran different simulations depending on the different possible compositions of Ahuna Mons, from 100 percent made of water ice to just about 40 percent. The estimated rate for the ice volcano to be flattening out is between 10 to 50 meters (30 to 160 feet) per million years.
“Ahuna Mons is at most 200 million years old. It just hasn’t had time to deform,” Sori said.
The surface of the dwarf planets could still be hiding the leftovers of several of these bygone cryovolcanos. And they might be able to be seen in the Dawn data.
“It would be fun to check some of the other features that are potentially older domes on Ceres to see if they fit in with the theory of how the shapes should viscously evolve over time,” Kelsi Singer, a Southwest Research Institute who studies frozen who was not involved with this research, stated. “Because all of the putative cryovolcanic features on other worlds are different, I think this helps to expand our inventory of what is possible.”
Ceres is located between Mars and Jupiter in the Asteroid Belt. It’s the only dwarf planet in the inner Solar System and the closest world to the Sun to have ice volcanoes, so it might behave differently to what astronomers have observed elsewhere.