A Search For Water Vapor Plumes On Europa Using SOFIA

HST transit images nearest in time to the SOFIA EXES observations. From left to right, 3/12/17 (2.7 days), 5/26/17 (1.0 days), 6/12/17 (16.7 days). HST images have Europa-north up, trailing hemisphere to the left, against the smooth background of Jupiter. The leftmost image is closest to the leading hemisphere SOFIA observation, while the central image is closest to the trailing hemisphere SOFIA observation.

We present mid-infrared SOFIA/EXES spectroscopy of Europa, seeking direct evidence of the presence of water vapor arising from plumes venting from the surface of Europa.

We place quantitatively useful upper limits on the strength of water vibrational-rotational emission lines. Conversion to water mass limits is dependent on the rotational temperature of the vapor. For low rotational temperature, the limits lie below the inferred water mass from previous HST plume observations. For higher temperatures, the limits are comparable. We also present coordinated HST transit observations obtained close in time to the SOFIA observations.

There is evidence for a feature close to the location of the previously seen feature north of the crater Pwyll in one of the HST images, although it was not observable by EXES given its location. We conclude that if a water plume had been active at the time of the SOFIA observation, with the strength implied by previous HST observations, then under the right Earth atmospheric and geometric conditions, the plume could have been detected by EXES, however no IR water vibrational-rotational emission was detected.

William Sparks, M. Richter, C. deWitt, E. Montiel, N. Dello Russo, J. Grunsfeld, M. A. McGrath, H. Weaver, K.P. Hand, E. Bergeron, W. Reach
(Submitted on 1 Jan 2019)

Comments: Accepted by Astrophysical Journal Letters, Dec. 26, 2018
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1901.00086 [astro-ph.EP] (or arXiv:1901.00086v1 [astro-ph.EP] for this version)
Submission history
From: Melissa A. McGrath
[v1] Tue, 1 Jan 2019 03:54:54 UTC (799 KB)

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