A strong seasonal dependence in the Martian hydrogen exosphere. Issue 20 (21st October 2015)

• Record Type: Journal Article
• Authors: Bhattacharyya, Dolon; Clarke, John T.; Bertaux, Jean‐Loup; Chaufray, Jean‐Yves; Mayyasi, Majd
• Is Part Of: Geophysical research letters. Volume 42:Issue 20(2015:Oct.)
• Page Start: 8678
• Page End: 8685
• Publication Date: 2015-10-21
• Subjects: Mars -- exosphere -- hydrogen -- seasons; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL065804
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Hubble Space Telescope and Mars Express observed unexpected rapid changes in the Martian hydrogen exosphere involving a decrease in scattered Lyman α intensity in fall 2007 (solar longitude, Ls = 331°–345°). These changes detected were speculated to be a combination of seasonal variation and/or dust storms and lower atmospheric dynamics. Here we present Hubble Space Telescope observations of Mars in 2014 over a broad range of heliocentric distances and seasons ( Ls = 138°–232°) which indicate a factor of ~3.5 change in Martian Lyman α brightness associated with a factor of ~5.4 variation of hydrogen escape flux in the absence of global dust storms and significant solar variability. We thus conclude that seasonal effects have a strong influence on the hydrogen exosphere, which in turn has major implications for the processes that control water supply to the Martian upper atmosphere and the history of water escape from Mars. Key Points: Strong variation of hydrogen density and escape from Mars is reported Strong seasonal variation observed in 2014 during low dust activity Mars water escape history depends on understanding these variations