Detection of Callisto’s oxygen atmosphere with the Hubble Space Telescope

Cunningham, N.; Spencer, J. R.; Feldman, P. D.; Strobel, D. F.; Osterman, Steven N.

doi:10.1016/j.icarus.2015.03.021

Cited by 54 publications

(106 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Lyman α albedo values derived in our model fit are somewhat higher than the FUV albedos found in the same STIS observations at 1380–1700 Å (1.6%/2.0%) [ Strobel et al , ] and also higher than the albedo values derived from HST/COS observations at 1335 Å (1.90%/2.08 %) [ Cunningham et al , ]. The relative ∼30% higher albedo on the trailing side compared to the leading side we find is similar to the difference in the FUV albedo found by Strobel et al [].…”

Section: Discussionsupporting

confidence: 88%

“…Recently, Hartkorn et al [] applied a fluid‐kinetic model to calculate ionization and excitation in a prescribed neutral O 2 , H 2 O, and CO 2 atmosphere. By comparison with both the ionosphere measurements and the detected oxygen emissions, their model results suggest a strong day‐night asymmetry in the atmosphere and an average dayside O 2 column density of ∼2 × 10 15 cm −2 based on the measurements of Cunningham et al [] and Kliore et al []. According to these models, H 2 O is expected to play a significant role in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Detection of a hydrogen corona at Callisto

et al. 2017

View full text Add to dashboard Cite

In December 2001, the Space Telescope Imaging Spectrograph of the Hubble Space Telescope obtained far‐ultraviolet spectral images of Jupiter's moon Callisto. The leading and trailing hemispheres were observed in the spectral range 1190 Å to 1720 Å when the moon was at eastern and western elongations, respectively. We analyzed the hydrogen Lyman α (1216 Å) signal in the two observations and found that faint atmospheric emissions extending up to several moon radii away are present in addition to the solar flux reflected off the surface. We show that the detected atmospheric Lyman α emissions are consistent with an escaping hydrogen corona with a vertical column density in the range of (6–12) ×1011 cm−2. The derived hydrogen abundance is about 2 times higher when the moon is at eastern elongation, possibly related to increased water sublimation when the visibly darker leading hemisphere is illuminated by the Sun. The detected hemispheric difference is larger than the measurement uncertainties providing first evidence for variations in Callisto's neutral atmosphere.

show abstract

Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Detection of a hydrogen corona at Callisto

et al. 2017

View full text Add to dashboard Cite

show abstract

“…At large bodies, such as Earth's Moon or the larger moons of the outer planets, many neutral species are ejected with velocities below escape speed and thus remain bound, forming so‐called surface‐bounded exospheres. To date, such neutral exospheres have been detected via a variety of methods at Mercury [e.g., Potter and Morgan , , ; McClintock et al , ], the Moon [ Hoffman et al , ; Feldman et al , ; Stern et al , ; Benna et al , ], the Galilean satellites [e.g., Hall et al , ; Carlson , ; Feldman et al , ; Cunningham et al , ], and some of the Saturnian satellites [ Teolis et al , ; Tokar et al , ]. Neutral coronae around bodies too gravitationally weak to keep ejected neutrals bound have also been theorized yet not detected to date; these objects include asteroids [e.g., Morgan and Killen , ; Schläppi et al , ; Altwegg et al , ] and Mars' moons Phobos and Deimos [ Soter , ; Mura et al , ; Cipriani et al , ].…”

Section: Introductionmentioning

confidence: 99%

The Phobos neutral and ionized torus

2016

View full text Add to dashboard Cite

Charged particle sputtering, micrometeoroid impact vaporization, and photon-stimulated desorption are fundamental processes operating at airless surfaces throughout the solar system. At larger bodies, such as Earth's Moon and several of the outer planet moons, these processes generate tenuous surface-bound exospheres that have been observed by a variety of methods. Phobos and Deimos, in contrast, are too gravitationally weak to keep ejected neutrals bound and, thus, are suspected to generate neutral tori in orbit around Mars. While these tori have not yet been detected, the distribution and density of both the neutral and ionized components are of fundamental interest. We combine a neutral Monte Carlo model and a hybrid plasma model to investigate both the neutral and ionized components of the Phobos torus. We show that the spatial distribution of the neutral torus is highly dependent on each individual species (due to ionization rates that span nearly 4 orders of magnitude) and on the location of Phobos with respect to Mars. Additionally, we present the flux distribution of torus pickup ions throughout the Martian system and estimate typical pickup ion fluxes. We find that the predicted pickup ion fluxes are too low to perturb the ambient plasma, consistent with previous null detections by spacecraft around Mars.

show abstract

“…Moreover, a recent study based on the analysis of HST data by Cunningham et al (2015) provided evidence that Callisto has a significant atmosphere, which is probably denser than that of Europa or Ganymede and thus probably exceeded in mass among Solar System satellites only by the atmospheres of Io, Triton and Titan. The O 2 atmosphere was found to be fully collisional even on the illuminated leading side of the moon, capable of supporting winds and other dynamical phenomena, protecting the surface from sputtering by magnetospheric particles.…”

Section: à2mentioning

confidence: 99%

“…6 See Hall et al (1998), Feldman et al (2000, Barth et al (1997). 7 See Carlson (1999), Cunningham et al (2015). 8 See Waite et al (2006).…”

Section: A Synthetic View Of Space Weather All Over the Solar Systemmentioning

confidence: 99%

Planetary space weather: scientific aspects and future perspectives

Plainaki

Lilensten

Radioti

et al. 2016

J. Space Weather Space Clim.

View full text Add to dashboard Cite

In this paper, we review the scientific aspects of planetary space weather at different regions of our Solar System, performing a comparative planetology analysis that includes a direct reference to the circum-terrestrial case. Through an interdisciplinary analysis of existing results based both on observational data and theoretical models, we review the nature of the interactions between the environment of a Solar System body other than the Earth and the impinging plasma/radiation, and we offer some considerations related to the planning of future space observations. We highlight the importance of such comparative studies for data interpretations in the context of future space missions (e.g. ESA JUICE; ESA/JAXA BEPI COLOMBO). Moreover, we discuss how the study of planetary space weather can provide feedback for better understanding the traditional circumterrestrial space weather. Finally, a strategy for future global investigations related to this thematic is proposed.

show abstract

Detection of Callisto’s oxygen atmosphere with the Hubble Space Telescope

Cited by 54 publications

References 38 publications

Detection of a hydrogen corona at Callisto

Detection of a hydrogen corona at Callisto

The Phobos neutral and ionized torus

Planetary space weather: scientific aspects and future perspectives

Contact Info

Product

Resources

About