Water Production by Comet 103P/Hartley 2 Observed with the SWAN Instrument on the SOHO Spacecraft

TL;DR

This study measures the water production rates of comet 103P/Hartley 2 using Lyman-alpha emissions observed by the SWAN instrument on SOHO, revealing variations around perihelion and contributions from icy fragments.

Contribution

First to quantify water production of 103P/Hartley 2 using SWAN data during 2010, including effects of icy fragments and activity variations around perihelion.

Findings

Water production was three times lower than in 1997.

Production increased by 2.5 times within one day on September 30, 2010.

Significant water release from icy fragments contributed up to 90%.

Abstract

Global water production rates were determined from the Lyman-{\alpha} emission of hydrogen around comet 103P/Hartley 2, observed with the SWAN (Solar Wind ANisotropies) all-sky camera on the SOHO spacecraft from September 14 through December 12, 2010. This time period included the November 4 flyby by the EPOXI spacecraft. Water production was 3 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 {\pm}20 days of perihelion was ~0.5 km^2, about half of the mean cross section of the nucleus. Outside this period it was ~0.2 km^2. The peak value was 90%, implying a significant water production by released nucleus icy fragments.