Credit: NASA and JPL
Vesta, the second-largest asteroid in the Solar System, is Vesta. It orbits the sun between Jupiter and Mars, with a diameter of approximately 330 miles.
Space fascination has been a long-standing part of the history of asteroids. "Marooned Off Vesta" was Isaac Asimov's first published story. It appeared in Amazing Stories, March 1939.
Christian Klimczak is associate professor at the Franklin College of Arts and Sciences' department of geology. "When we think of Asteroid Belts, we probably imagine Han Solo driving the millennium falcon through densely shaped gray rock formations in space," he said. Although most rocks are irregularly shaped and grey, NASA's Dawn spacecraft was able to navigate around them to reach Vesta.
NASA launched Dawn in September 2007 as a space probe with the mission to study Vesta and Ceres, two of three protoplanets within the asteroid belt.
Vesta is made up of rock in its crust, mantle and core, much like Earth. It also has an iron core. It is considered a planetesimal due to its size (for an asteroids) and the fact that Vesta has a core, crust, and mantle. Planetesimals are the building blocks from which planets are made. Earth was formed through the accretion several of these planetesimals. Klimczak stated that Vesta was also on its way to becoming an Earth-like world, but that planet formation stopped at a very early stage in the history our solar system's history. Studying Vesta allows us to understand how our planet formed in the early days of the solar system.
Klimczak co-authored a new study on large-scale impact basins and troughs on Vesta.
Is it Vesta's giant troughs that created them?
Vesta was also hit by two large asteroids, which created large impact craters that covered most of Vesta's southern hemisphere. These impacts are believed to have sent rocky material into space. Scientists now have Vesta rock samples to study the geochemistry of Vesta's meteorites, which some of these rocks may have reached Earth as meteorites.
Jupiter Cheng, a doctoral candidate in geography and co-author of the study, said that rock properties are affected by environmental conditions such as surrounding stresses and water. Vesta is smaller than Earth or the moon. Because of this, rock would behave differently at the surface.
Cheng says that one of the big questions is how these large troughs were formed. These two troughs are located around Rheasilvia (and Veneneia) respectively. They are widely believed to have been formed simultaneously by impact events. However, this assumption has never been proven.
Cheng stated that his research used crater-counting methods to determine the relative age of the basins, and troughs. Crater counting, which is an accepted method of estimating the age a planet's surface is used to estimate its age. It is based on the assumption that if a piece is new then there are no impact craters. Impact craters accumulate at a rate that is known.
She explained that counting the number of different-sized craters in an area can help us determine the age of the surface and how long it has been accumulated. Our results show that both the basins and troughs have similar numbers of craters of different sizes. This indicates that they are of similar age. The uncertainties in the counts of craters allow the formation of troughs long after impacts.
Since long, the origin of the troughs is a subject of speculation within the scientific community. Klimczak believes that their geologic evidence will support a more durable theory about Vesta's troughs.
The September issue of Icarus contains the study.
In a forthcoming paper, a new theory will be presented
The leading hypothesis is that these troughs are fault bound valleys that have a distinct scarp at each end that mark the down-drop or sliding of a block. Cheng said that rock can also fracture and form such troughs. This is a new origin, which she is currently investigating as part of her UGA dissertation.
She stated that Vesta's gravity does not cause sliding to occur at shallow depths. Instead, physics indicates that rocks there are more likely to fracture apart. According to the scientific community, crack opening is the only way these troughs could form. The overall project offers alternatives to Vesta's geological history and trough origin. These results are important for understanding similar landforms elsewhere in the solar system.
Continue reading Study of mesosiderite Zircons suggests Vesta was struck with a very large stone
Further information: Hiu Ching Jou Cheng et.al, Age relationships between large-scale impact basins and troughs on Vesta. Icarus (2021). Information from the Journal: Icarus HiuChing Jupiter Cheng, Age relationships between large-scale troughs, and impact basins, Vesta, (2021). DOI: 10.1016/j.icarus.2021.114512
