What a difference a planetary overflight makes. Charon, the moon of Pluto, which was once only a blurred mass of pixels adjacent to a larger drop, now has its first geological map, published in AGU Journal of Geophysical Research: planets.
The new map was based on data and imagery gathered during the 2015 survey of the New Horizons spacecraft, which has collected enough data to map about a third of Charon's surface.
In this region, scientists have identified 16 types of different geological units, or areas with similar landscapes, as well as 10 km high cliffs; more than a thousand grooves and other long, linear features; and a patchwork of light and dark earth.
To obtain elevations of cliffs, valleys, craters and other features, the team used several Charon images taken during the passage of the spacecraft to create three-dimensional stereo images. These images are taken from different positions. They can therefore be treated according to the same principle used by our brain to take images from two eyes and give us a perception of depth.
The new map shows the possible evidence of a world that may have once opened up as a cracked lip or a rising cake, and then released frozen materials from within to invade large areas called cryoflows. In fact, researchers have discovered that Charon is perhaps one of the most convincing examples of large cryoflowers found in the solar system so far.
The new map revealed many surprising features of Charon, including its craters.
"Surprisingly, we see very, very few degraded craters," said Stuart Robbins of the Southwest Research Institute and lead author of the new paper. "On Mars, we see old (degraded) and new craters." On Charon, almost every crater we see appears to have been created recently. " This or the craters they see have existed for a long time without anything changing them, he added.
An explanation for the absence of craters of aging appearance could be that some process has erased the older craters. This process can be ancient ice flows – cryoflows – that gush through cracks on the surface of Charon and bury the old craters.
If this is the case, it is possible that sometimes in Charon's past, his interior has warmed up and has undergone a chemical or physical change that has caused it to spread slightly. This expansion cracked the surface – in the same way that the surface of a cake cracks when the cake rises during cooking, explained Robbins. Then, warmer materials from below flowed to the surface of Charon. This material would have hidden a large part of Charon's original surface, as well as craters that were found there. This would also explain features that resemble broken blocks of the lunar crust captured and surrounded by a stream of cooler materials.
Oz, Vulcan and Spock
To organize the characteristics of Charon on the basis of cryoflux, the authors of the map have described and named three great periods of the history of Charon: Ozian, Vulcanian and Spockian.
The Ozian era was more than 4 billion years ago, when the informally named Oz Terra part of the Charon crust was formed, shown in the upper part of the map.
The Vulcanian arrived then, there is perhaps more than 4 billion years ago, with cryoflux forming the Vulcan planum in the lower part of the map, near the Equator of Charon. The Vulcanian probably continued for a while while different parts of Charon were cooling down.
The final epoch, the Spockian, represents the time after the solidification of the Vulcan Palum. This is the period during which the same area was covered with craters of impact, until today.
This is just a possible conspiracy for Charon's story, Robbins points out.
"We could be absolutely wrong," he said of cryofilms.
This is a problem that planetary scientists can solve while waiting for more data from Charon, which may be very long, since no follow-up mission is currently underway in this part far away from the system. solar.
Image: The youngest crater in Charon?
Stuart J. Robbins et al. Geological relief and chronostratigraphic history of Charon revealed by a hemispheric geological map, Journal of Geophysical Research: Planets (2019). DOI: 10.1029 / 2018JE005684