A geological map of the giant asteroid Vesta

Geological map of the giant asteroid Vesta. Brown colors represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively (Image NASA/JPL-Caltech/ASU)
Geological map of the giant asteroid Vesta. Brown colors represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively (Image NASA/JPL-Caltech/ASU)

A little over a year ago, an atlas of the giant asteroid Vesta was presented but the analysis of the data collected by the Dawn space probe went even further. A special issue of the journal “Icarus” was all about Vesta presenting a series of geological maps that show details never seen before the characteristics of its surface.

David Williams of the School of Earth and Space Exploration at Arizona State University led a team of 14 researchers in a task that lasted about two and a half years. The team used the photographs taken by NASA’s Dawn spacecraft when it spent more than one year orbiting Vesta to create a geological map.

Vesta is probably a protoplanet that couldn’t complete its development due to the interference of Jupiter’s gravity. It’s exactly for this reason that it’s so interesting, a kind of fossil of the early history of the solar system. Unlike other celestial bodies such as some comets or some asteroids, which have remained almost unchanged for a few billions of years, Vesta suffered several impacts because it’s part of the asteroid belt between Mars and Jupiter.

All of that makes Vesta worthy of the many thorough studies carried out in recent years. In the case of this geological study, the researchers studied the surface of the giant asteroid to determine the chronology of events that made it what we see through the photos of the Dawn space probe.

This work was made difficult by the fact that the researchers had only images available, not Vesta’s soil samples. For this reason they developed models based on the frequency of impacts on the Moon and asteroids. The conclusion is that the crust of Vesta has an age between 2.1 (according to the asteroids model) and 3.7 billion years (according to the lunar model).

Vesta has three very large craters. The age of the crater Rheasilvia has been estimated between 1 and 3.5 billion years, depending on the model applied. The age of Veneneia is estimated between 2 and 3.7 billion years. The age of Marcia crater is estimated between 120 and 390 million years, which means that it’s fairly recent in geological terms. Therefre those are far from accurate estimates showing that the models have to be adapted to an object different from normal asteroids and the Moon.

The researchers, however, were able to create a geological map of Vesta using panchromatic images obtained by the Dawn space probe’s framing camera. It also provided a context for a lot of information obtained by the VIR (Visual and infrared spectrometer) and Grand (Gamma Ray and Neutron Detector) instruments.

This and other research on Vesta can be difficult to understand because it’s an asteroid really far away. They’re important because the nature and history of the protoplanet left there many signs of the solar system’s history. Studying Vesta, scientists are learning something new about the formation of planets in general and those of the solar system in particular.

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