Water production by comet 103P/Hartley 2 observed with the SWAN instrument on the SOHO spacecraft

Abstract

Global water production rates were determined from the Lyα emission of hydrogen around comet 103P/Hartley 2, observed with the SWAN (Solar Wind Anisotropies) all-sky camera on the SOHO spacecraft from 2010 September 14 through December 12. This time period included the November 4 flyby by the EPOXI spacecraft. Water production was three times lower than during the 1997 apparition also measured by SWAN. In 2010, it increased by a factor of 2.5 within one day on September 30 with a similar corresponding drop between November 24 and 30. The total surface area of sublimating water within 20 days of perihelion was 0.5km2, about half of the mean cross section of the nucleus. Outside this period it was 0.2km2. The peak value was 90%, implying a significant water production by released nucleus icy fragments. © 2011. The American Astronomical Society. All rights reserved.