Atmosphere and water loss from early mars under extreme solar wind and extreme ultraviolet conditions

Naoki Terada, Yuri N. Kulikov, Helmut Lammer, Herbert I.M. Lichtenegger, Takashi Tanaka, Hiroyuki Shinagawa, Tielong Zhang

研究成果: Article査読

67 被引用数 (Scopus)


The upper limits of the ion pickup and cold ion outflow loss rates from the early martian atmosphere shortly after the Sun arrived at the Zero-Age-Main-Sequence (ZAMS) were investigated. We applied a comprehensive 3-D multi-species magnetohydrodynamic (MHD) model to an early martian CO 2-rich atmosphere, which was assumed to have been exposed to a solar XUV [X-ray and extreme ultraviolet (EUV)] flux that was 100 times higher than today and a solar wind that was about 300 times denser. We also assumed the late onset of a planetary magnetic dynamo, so that Mars had no strong intrinsic magnetic field at that early period. We found that, due to such extreme solar wind-atmosphere interaction, a strong magnetic field of about ∼4000 nT was induced in the entire dayside ionosphere, which could efficiently protect the upper atmosphere from sputtering loss. A planetary obstacle (∼ ionopause) was formed at an altitude of about 1000 km above the surface due to the drag force and the mass loading by newly created ions in the highly extended upper atmosphere. We obtained an O+ loss rate by the ion pickup process, which takes place above the ionopause, of about 1.5 × 1028 ions/s during the first ≤150 million years, which is about 104 times greater than today and corresponds to a water loss equivalent to a global martian ocean with a depth of ∼8 m. Consequently, even if the magnetic protection due to the expected early martian magnetic dynamo is neglected, ion pickup and sputtering were most likely not the dominant loss processes for the planet's initial atmosphere and water inventory. However, it appears that the cold ion outflow into the martian tail, due to the transfer of momentum from the solar wind to the ionospheric plasma, could have removed a global ocean with a depth of 10-70 m during the first ≤150 million years after the Sun arrived at the ZAMS.

出版ステータスPublished - 2009

ASJC Scopus subject areas

  • 農業および生物科学(その他)
  • 宇宙惑星科学


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