The appearance of a 'fresh' surface on 596 Scheila as a consequence of the 2010 impact event

TL;DR

The 2010 impact on asteroid 596 Scheila exposed fresh material, causing a spectral slope change from moderately red to red, confirming space weathering effects on similar asteroids and indicating a larger population of outer solar system objects in the main belt.

Contribution

This study provides the first telescopic evidence of spectral slope change due to impact-induced surface refreshing on a primitive asteroid.

Findings

Spectral slope changed from T-type to D-type after impact.

Supports models of space weathering reducing redness over time.

Suggests a larger population of outer solar system objects in the main belt.

Abstract

Dust emission was detected on main-belt asteroid 596 Scheila in December 2010, and attributed to the collision of a few-tens-of-meters projectile on the surface of the asteroid. In such impact, the ejected material from the collided body is expected to mainly comes from its fresh, unweathered subsurface. Therefore, it is expected that the surface of 596 was partially or entirely refreshed during the 2010 impact. By combining spectra of 596 from the literature and our own observations, we show that the 2010 impact event resulted in a significant slope change in the near-infrared (0.8 to 2.5 {\mu}m) spectrum of the asteroid, from moderately red (T-type) before the impact to red (D-type) after the impact. This provides evidence that red carbonaceous asteroids become less red with time due to space weathering, in agreement with predictions derived from laboratory experiments on the primitive Tagish Lake meteorite, which is spectrally similar to 596. This discovery provides the very first telescopic confirmation of the expected weathering trend of asteroids spectrally analog to Tagish Lake and/or anhydrous chondritic porous interplanetary dust particles. Our results also suggest that the population of implanted objects from the outer solar system is much larger than previously estimated in the main-belt, but many of these objects are hidden below their space-weathered surface.