Evidence for an impact event on main-belt asteroid Griseldis

University of Hawaii at Manoa's Institute for Astronomy Press Release

13 November 2015 Astronomy Now

The top three panels are three different exposures with the 8-metre Subaru Telescope showing asteroid (493) Griseldis moving from left to right as you move from the first panel to the third. The bottom panel shows all three exposures added together, after suppressing the galaxy that interferes with the "tail" in the first exposure; the asteroid is on the right. Image credit: D. Tholen, S. Sheppard, C. Trujillo.
The top three panels are three different exposures with the 8-metre Subaru Telescope showing asteroid (493) Griseldis moving from left to right as you move from the first panel to the third. The bottom panel shows all three exposures added together, after suppressing the galaxy that interferes with the “tail” in the first exposure; the asteroid is on the right. Image credit: D. Tholen, S. Sheppard, C. Trujillo.
The main-belt asteroid (493) Griseldis, that lies between the orbits of Mars and Jupiter, was probably hit by another object last March. The results were reported on 12 November at the 47th Annual Meeting of the Division for Planetary Sciences of the American Astronomical Society near Washington, DC.

Observations taken with the 8-metre Subaru Telescope on Maunakea on 17 March 2015 UT showed that the asteroid had “an extended feature,” which is astronomer-speak for a tail.

However, unlike the tails of comets, which flow in the direction opposite from the Sun due to the solar wind, the extension on Griseldis was not in the antisolar direction, and the extension proved to be a short-lived phenomenon.

Additional observations taken with the 6.5-metre Magellan Telescope four nights later still detected the extension, though it was weaker, but exposures taken with the 2.2-metre University of Hawaii telescope on 24 March UT or Magellan on 18 April UT and 21 May UT showed no such feature, nor did images from telescope archives taken in 2010 and 2012.

The researchers, David Tholen (Institute for Astronomy, University of Hawaii at Manoa), Scott Sheppard (Carnegie Institution), and Chad Trujillo (Gemini Observatory) have therefore concluded that “the observations are consistent with the occurrence of an impact event on this asteroid.”

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