User:Aleaton02/Exosphere
The Exosphere of Mercury[edit]
Many hypotheses exist about the formation of the surface boundary exosphere of Mercury, which has been noted to include elements such as sodium (Na), potassium (K), and calcium (Ca)[1]. Each material has been suggested as a result of processes such as impacts, solar wind, and degassing from the terrestrial body that cause the atoms or molecules to form the planet’s exosphere[1].
Meteoroids have been reported to commonly impact the surface of Mercury at speeds ranging up to 80 km/s, which are capable of causing vaporization of both the meteor and surface regolith upon contact[2]. These expulsions can result in clouds of mixed materials due to the force of the impact, which are capable of transporting gaseous materials and compounds to Mercury’s exosphere. During the impact, the former elements of the colliding bodies are mostly devolved into atoms rather than molecules that can then be reformed during a cooling, quenching process. Such materials have been observed as Na, NaOH, and O2 [2]. However, it is theorized that, though different forms of sodium have been released into the Mercury exosphere via meteor impact, it is a small driver for the concentration of both sodium and potassium atoms overall[2]. Calcium is more likely to be a result of impacts, though its transport is thought to be completed through photolysis of its former oxides or hydroxides rather than atoms released during the moment of impact such as sodium, potassium, and iron (Fe)[2].
Another possible method of the exosphere formation of Mercury is due to its unique magnetosphere and solar wind relationship. The magnetosphere of this celestial body is hypothesized to be an incomplete shield from the weathering of solar wind. If accurate, there are openings in the magnetosphere in which solar wind is able to surpass the magnetosphere, reach the body of Mercury, and sputter the components of the surface that become possible sources of material in the exosphere[3]. The weathering is capable of eroding the elements, such as sodium, and transporting them to the atmosphere. However, this occurrence is not constant, and this is unable to account for all atoms or molecules of the exosphere[4].
- ^ a b Leblanc, F.; Chassefière, E.; Johnson, R. E.; Hunten, D. M.; Kallio, E.; Delcourt, D. C.; Killen, R. M.; Luhmann, J. G.; Potter, A. E.; Jambon, A.; Cremonese, G.; Mendillo, M.; Yan, N.; Sprague, A. L. (2007-06-01). "Mercury's exosphere origins and relations to its magnetosphere and surface". Planetary and Space Science. Highlights in Planetary Science. 55 (9): 1069–1092. doi:10.1016/j.pss.2006.11.008. ISSN 0032-0633.
- ^ a b c d Berezhnoy, Alexey A.; Klumov, Boris A. (2008-06-01). "Impacts as sources of the exosphere on Mercury". Icarus. 195 (2): 511–522. doi:10.1016/j.icarus.2008.01.005. ISSN 0019-1035.
- ^ Potter, A. E.; Morgan, T. H. (1990-05-18). "Evidence for Magnetospheric Effects on the Sodium Atmosphere of Mercury". Science. 248 (4957): 835–838. doi:10.1126/science.248.4957.835. ISSN 0036-8075.
- ^ Killen, R. M.; Potter, A. E.; Reiff, P.; Sarantos, M.; Jackson, B. V.; Hick, P.; Giles, B. (2001-09-25). "Evidence for space weather at Mercury". Journal of Geophysical Research: Planets. 106 (E9): 20509–20525. doi:10.1029/2000JE001401. ISSN 0148-0227.