Scientists peers beneath Ceres' surface with help from Dawn spacecraft
NASA scientists have taken their first look at the interior of the dwarf planet Ceres, by tracking tiny alterations in the motion of the Dawn spacecraft as it continues to orbit the enigmatic planetoid. These gravitational readings, when paired with the detailed surface data harvested by Dawn, will allow scientists to gain a more comprehensive picture of Ceres' history.
Since arriving in orbit around Ceres in March 2015, Dawn has transmitted countless haunting images ofthe dwarf planet's barren, cratered landscape. While we have learned a great deal from these images andfurther data collected from the advanced suite of scientificinstruments situated aboard the probe, we have quite literally only beenscratching the surface.
A newstudy led by scientists from NASA's Jet Propulsion Laboratory (JPL) has succeeded in plumbing the depths ofCeres' interior, by analyzing minute alterations in the motion ofDawn as it orbits the dwarf planet.
Anyspacecraft in orbit around a solar system body is subject to thatobject's gravitational pull. A number of factors, includingvariations in surface height or the density and distribution of thematerials that make up the interior of a celestial body, can causesubtle perturbations in the motion of an orbiting spacecraft.
NASAis capable of tracking Dawn's orbital velocity to within 0.004 inches(0.1 mm) of its actual speed by monitoring radio tracking data sentbetween the probe and the agency's Deep Space Network.The team behind the study was able to analyze these radio signals and isolate orbital alterationscaused by variations in Ceres' gravitational field, and byreconciling these gravitational readings with surface observationsalready collected by the probe, glean insights regarding thecomposition and structure of the dwarf planet.
Itwas discovered that Ceres' overall density is significantly weakerthan that of other rocky solar system bodies such as Earth, Mars andthe asteroid Vesta,which had been Dawn's previous scientific target. According to the analysisof Ceres' gravitational field, it is likely that the dwarf planet isstructured in compositionally distinct layers much like Earth, albeitnot as well defined.
Thedensest material on Ceres is located at the planetoid's core, while lighter materialssuch as water ice are thought to have partially separated from denserrocky material during a heating phase that occurred relatively soonafter the creation of the dwarf planet. The lighter matter thengravitated toward the surface to form the planet's outer layers.
Thestudy also confirmed that the structure of Ceres' interior isdictated by the dwarf planet's rotation, thanks to a propertyreferred to as hydrostatic equilibrium, which had been theorized toinfluence Ceres, but had not been confirmed prior to the study.
Thestructurally weak nature of Ceres' upper layers causes high elevationfeatures such as the isolated Ahuna Mons to displace material in the planetoid's mantle, much like a large ship would displace water in Earth'soceans. According to the scientists behind the study, it is likely that subsurface water was mobile on ancient Ceres, and that the dwarf planet's interior did not reach sufficient temperatures to melt silicates, and give the planetoid a metallic core.
Bycombining insights of Ceres' internal structure with the detailed surface analysis carried out by the Dawn spacecraft, scientists canbegin to unravel more of the complex formation processes that sculpted the desolate dwarf planet that we see today.