Hubble Space Telescope observations of active asteroid 324P/La Sagra near perihelion show continued mass loss consistent with the sublimation of near-surface ice. Isophotes of the coma measured from a vantage point below the orbital plane are best matched by steady emission of particles having a nominal size. of. a similar to 100 mu m. The inferred rate of mass loss, dM(d)/dt similar to 0.2 kg s(-1), can be supplied by sublimation of water ice in thermal equilibrium with sunlight from an area as small as 930 m(2), corresponding to about 0.2% of the nucleus surface. Observations taken from a vantage point only 0.degrees 6. from the orbital plane of 324P set a limit to the velocity of ejection of dust in the direction perpendicular to the plane, V-perpendicular to < 1 m s(-1). Short-term photometric variations of the near-nucleus region, if related to rotation of the underlying nucleus, rule-out periods <= 3.8 hr and suggest that rotation probably does not play a central role in driving the observed mass loss. We estimate that, in the previous orbit, 324P lost about 4 x 10(7) kg in dust particles, corresponding to 6 x 10(-5) of the mass of a 550 m spherical nucleus of assumed density rho = 1000 kg m(-3). If continued, mass loss at this rate would limit the lifetime of 324P to similar to 1.6 x 10(4) orbits (about 10(5) years). To survive for the 100-400 Myr timescales corresponding to dynamical and collisional stability requires a duty cycle of 2 x 10(-4) <= f(d) <= 8 x 10(-4). Unless its time in orbit is overestimated by many orders of magnitude, 324P is revealed as a briefly active member of a vast population of otherwise dormant ice-containing asteroids.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/621499 |
| Date | 06 September 2016 |
| Creators | Jewitt, David, Agarwal, Jessica, Weaver, Harold, Mutchler, Max, Li, Jing, Larson, Stephen |
| Contributors | Univ Arizona, Lunar & Planetary Lab |
| Publisher | IOP PUBLISHING LTD |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | © 2016. The American Astronomical Society. All rights reserved. |
| Relation | http://stacks.iop.org/1538-3881/152/i=3/a=77?key=crossref.af50767ce1dc6cbe27b13be980ddfb3c |
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