A study of gas productivity of Comet 103P/Hartley 2
Abstract
In order to support and complement space-based measurements of the gas and dust productivity of comets taken during a limited time period, we have made a combined study of the coma activity of Comet 103P/Hartley 2 for the 1991, 1997, and 2010 apparitions. We quantify the presence of the gas through its water production rate (in molecules s$ ^{-1}$) using the Semi-Empirical Method of Visual Magnitudes SEMVM), and its subsequent conversion into gas mass production rate (in g s$ ^{-1}$). This method also allows an analysis of the minimum nuclear size and active surface area. For the three apparitions that were analyzed, we verify that water (and gas) production rates increase with decreasing heliocentric distance r (au) inbound to perihelion with exponents [-6.21 (1991), -5.86 (1997), and -5.45 (2010)], and decrease with increasing r (au) post-perihelion with exponents [-4.75 (1991), -2.33 (1997), and -3.29 (2010)]. From these power-laws at perihelion, we verify that Hartley 2 has total gas mass loss rates of about (4200 - 5260), (1200 - 1440) and (340 - 405) kg s$ ^{-1}$ in 1991, 1997, and 2010. This method implies an active surface area of about 7$\pm$3, 2$\pm$0.9, and 0.4$\pm$0.2 km$ ^{2}$, consistent with mean minimum nucleus sizes of 0.75$\pm$0.3, 0.4$\pm$0.2, and 0.17$\pm$0.8 km, for these apparitions. For each apparition, correlations between water production rates and reduced visual magnitudes are obtained. Combining these power-laws (for total gas and radial velocity at pre- and post-perihelion), and assuming a nuclear density of 530 kg m$ ^{-3}$, we find that Hartley 2 lost $\sim$9%, 3%, and 1% of its volatile mass (orbit)$ ^{-1}$, respectively, and imply a minimum effective radius of $\sim$∼0.17 km for the nucleus of Hartley 2. Our results are in good agreement with those of the Deep Impact (EPOXI) Mission and other ground-based measurements. Acknowledgements: We greatly appreciate support from FAPESP (Grant No. 2015/03176-8, Brazil) and the NSF Planetary Astronomy Program (Grant No. 0908529, USA).
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.291B