Scientists using data returned by NASA’s Dawn spacecraft have found evidence of numerous landslides on the surface of the dwarf planet Ceres, which they view as evidence that the small world contains a significant amount of water ice.
Between 20 and 30 percent of all craters more than six miles (10 km) wide show evidence of landslides, which scientists believe were formed via “ground ice” processes that require a mix of rock and ice and to date have been found only on Earth and Mars.
Three separate types of landslides were identified as occurring on Ceres’ surface.
The first, known as Type 1, are round and resemble rocky glaciers and icy landslides in Earth’s Arctic region. Features that look like thick toes can be seen at the landslides’ edges.
As on Earth, most Type 1 landslides are located in Ceres’ upper latitudes, where the largest amount of ice is believed to be present near the small planet’s surface.
Most common on Ceres are Type 2 landslides, which are thin and long and found at the small world’s middle latitudes. These resemble avalanche deposits seen on Earth.
Seen largely at lower latitudes, Type 3 landslides appear to emerge from large impact craters. Scientists believe they formed when impacting objects melted ice at the impact sites.
Brittney Schmidt, Dawn Science Team Associate, and Georgia Tech Assistant Professor led the study, whose results are published in the journal Nature Geoscience.
“Landslides cover more area in the poles than at the equator, but most surface processes generally don’t care about latitude,” said Schmidt, who interprets the study as indicating Ceres’ subsurface is composed of a mix of ice and rock.
“That’s one reason we think it’s ice affecting the flow processes. There’s no other good way to explain why the poles have huge, thick landslides; mid-latitudes have a mixture of sheeted and thick landslides, and low altitudes have just a few.”
From the shape and distribution of Ceres’ landslides, the researchers estimate the volume of ice in its upper layers ranges between 10 and 50 percent.
“It’s just kind of fun that we see features on this small planet that remind us of those on the big planets, like Earth and Mars. It seems more and more that Ceres is our innermost icy world,” Schmidt said.