June 4, 2020

15.10.11: The Strange New World of Vesta.

Vesta’s south pole region as seen from Dawn’s framing camera. (Credit: NASA/JPL).

NASA’s Dawn spacecraft remains the mission that perhaps you’re not following, but should be… since entering orbit around the main belt asteroid 4 Vesta, the plucky ion-propelled spacecraft is returning some fairly mind-blowing images.  The asteroid/proto-planet/insert-current-favorite-definition is becoming a brave new world before our very eyes, the first dwarf planet we’ve orbited and reconnoitered in detail. What are those ridges? What caused intriguing features such as the overlapping crater doublet dubbed “the Snowman?” Already, discoveries on the tiny world-let are re-writing the book of solar system formation. One massive formation 9 miles high is taller than Everest and may turn out to be the largest mountain in the solar system known, vying with Mars’s Olympus Mons for the title. This isn’t surprising, as the gravity on Vesta is correspondingly low, and thus unable to crush or smooth out large features. (Solar system “mountains” are generally gauged by their deviation from a standard mean diameter or the surrounding plains, as a terrestrial version of “sea-level” doesn’t exist!)

But the best is still yet to come. Dawn’s entry into a lower altitude, or “mapping orbit” this past month of 420 miles over the terrain of Vesta is revealing the world as never before. Keep in mind, we actually have samples of Vesta in the form of asteroids right here on Earth; positive ID was gained by comparing spectral analysis of the space rocks. These will serve as an excellent “differential diagnosis” tool, and perhaps we’ll even be able to point to an impact region on Vesta soon and say “this meteorite came from that spot.”

Dawn orbits Vesta about every 12.3 hours, and “Vestian longitude” has been defined the meridian as 0° starting from the 500-meter crater Claudia. Next year in July, Dawn will fire its ion-engines and perform another first; it will depart the environs of Vesta for the king of the asteroid belt, arriving at Ceres in February 2015. What new discoveries await? Will Ceres look as ‘Phobos-like’ as Vesta? Any moonlets lurking out there? How ‘bout monoliths? Keep an eye on the Dawn mission; it’s returning some stunning science!


  1. [...] Launched in 2007 from Cape Canaveral Air Force Station, Dawn was the first spacecraft to orbit and explore the dwarf planet 4 Vesta from July 2011 before departing in September 2012 for Ceres. Dawn’s [...]

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