Detection of neutral sodium above Mercury  during the transit on 
 2003 May 7

Schleicher, H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.; Soltau, D.

doi:10.1051/0004-6361:20040477

Cited by 75 publications

(94 citation statements)

References 18 publications

(19 reference statements)

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“…Dawn/dusk asymmetry is also significant in the case of PSD as seen in Figure 4 panels b and f. This is the case because PSD dominates when the velocity of the terminator is maximum around Mercury's aphelion. In Figure 3, a clear dawn/dusk asymmetry is apparent between TAA=110° and 240° roughly where the PSD enhanced simulation predicts such an asymmetry and where Schleicher et al (2004) observed it (at TAA=150°).…”

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confidence: 77%

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AbstractOur understanding of Mercury's sodium exosphere has improved considerably in the last 5 years thanks to new observations (Schleicher et al 2004) and to the publication of a summary of the large set of ground based observations (Potter et al 2008;2007;. In particular, the non-uniformity in longitude of the dayside sodium distribution (the dawn/dusk asymmetry) has now been clearly observed.

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confidence: 99%

“…As an example, Killen and Ip (1999) discussed this possibility, arguing that sodium atoms would not have time to migrate from day to night sides because of their short residence time in Mercury's exosphere as compared to argon in the lunar exosphere. However, Schleicher et al (2004), observing the dependence of the exospheric sodium absorption feature on the solar flux during Mercury's transit of the Sun, demonstrated the existence of a strong asymmetry with a significantly denser exosphere at the dawn terminator than at the dusk terminator. This was later confirmed by Potter et al (2006) when analyzing the large set of data they compiled over six years of regular observations of Mercury.…”

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Mercury exosphere I. Global circulation model of its sodium component

Leblanc

Johnson

2010

Icarus

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Our understanding of Mercury's sodium exosphere has improved considerably in the last 5 years thanks to new observations (Schleicher et al. 2004) and to the publication of a summary of the large set of ground based observations (Potter et al. 2008;2007;. In particular, the non-uniformity in longitude of the dayside sodium distribution (the dawn/dusk asymmetry) has now been clearly observed. This suggests that Mercury's sodium exosphere is partly driven by a global day to night side migration of the volatiles. One of the key questions remaining is the nature of the prevailing sodium ejection mechanisms. Because of the uncertain parameters for each ejection mechanisms, solving this problem has been difficult as indicated by the numerous papers over the last 15 years with very different conclusions. In addition, the variation of the size and of the spatial distribution of the surface reservoir varies with distance from the sun affecting the importance of each ejection mechanism on Mercury's orbital position We here present an updated version of the model. We take into account the two populations of sodium in the surface reservoir , one ambient population (physisorbed in the regolith with low binding energy) and one source population (chemisorbed coming from grain interior or from fresh dust brought to the surface and characterized by a higher binding energy). We also incorporate a better description of the solar wind sputtering variation with solar conditions. The results of a large number of simulations of the sodium exosphere are compared with the measured annual cycle of Mercury sodium emission brightness. These measurements were obtained from the published data by Potter et al. (2007) as well as from our own data obtained during the last two years using THEMIS solar telescope. These data show that: the annual cycle in the emission brightness is roughly the same from one year to another; there are significant discrepancies ACCEPTED MANUSCRIPT3 between what would be observed if the exospheric content were constant; and t the annual cycle of Mercury's sodium exosphere strongly depends on its position in its orbit so that there are seasons in Mercury's exosphere.Based on these comparisons we derived the principal signatures for each ejection mechanism during a Mercury year and show that none of the ejection mechanisms dominates over the whole year. Rather, particular features of the annual cycle of the sodium intensity appear to be induced by one, temporarily dominant, ejection mechanism. Based on this analysis, we are able to roughly explain the annual cycle of Mercury's exospheric sodium emission brightness.We also derive a set of parameters defining those ejection mechanisms which best reproduce this cycle. For our best case, Mercury's exosphere content varies from ~1.6±0.1×10 28 Na atoms at TAA=140° and 70° respectively to ~4.5±0.3×10 28 Na atoms at TAA=180° and 0°. In addition, Mercury's exospheric surface reservoir contains ~1×10 31 Na atoms at TAA=300° and at TAA=170° with up to three times more so...

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Mercury exosphere I. Global circulation model of its sodium component

Leblanc

Johnson

2010

Icarus

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“…The ground-based observations by Bida et al (2000) reveal Ca I emission in the resonance line at 4226.74 Å. Observations performed during the transit of Mercury in 2003 detected additionally sodium emission lines (Na I D 1,2 ), which allowed Schleicher et al (2004) to trace the extent of the exosphere of Mercury above the planet's limb. Potter et al (2002) observed a sodium-tail in the anti-sunward direction extending ten's of planetary radii.…”

Section: The Mercury Analogymentioning

confidence: 99%

Constraints on the exosphere of CoRoT-7b

Guenther

Cabrera

Erikson

et al. 2010

A&A

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Context. The small radius and high density of implies that this transiting planet belongs to a different species than all transiting planets previously found. Current models suggest that this is the first transiting rocky planet found outside the solar system. Given that the planet orbits a solar-like star at a distance of only 4.5 R * , it is expected that material released from its surface may then form an exosphere. Aims. We constrain the properties of the exosphere by observing the planet in-and out-of-transit. Detecting the exosphere of CoRoT7b would for the first time allow us to study the material originating in the surface of a rocky extrasolar planet. We scan the entire optical spectrum for any lines originating from the planet, focusing particularly on spectral lines such as those detected in Mercury and Io in our solar system. Methods. Since lines originating in the exosphere are expected to be narrow, we observed CoRoT-7b at high resolution with UVES on the VLT. By subtracting the two spectra from each other, we search for emission and absorption lines originating in the exosphere of CoRoT-7b. Results. In the first step, we focus on Ca I, Ca II, and Na, because these lines have been detected in Mercury. Since the signal-to-noise ratio (S/N) of the spectra is as high as 300, we derive firm upper limits for the flux-range between 1.6 × 10 −18 and 3.2 × 10 −18 W m −2 . For CaO, we find an upper limit of 10 −17 W m −2 . We also search for emission lines originating in the plasma torus fed by volcanic activity and derive upper limits for these lines. In the whole spectrum we finally try to identify other lines originating in the planet. Conclusions. Except for CaO, the upper limits derived correspond to 2−6 × 10 −6 L * , demonstrating the capability of UVES to detect very weak lines. Our observations certainly exclude the extreme interpretations of data for CoRoT-7b, such as an exosphere that emits 2000 times as brightly as Mercury.

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“…For example, during the Mercury transit in 2003, neutral sodium in its exosphere was detected using this technique (Schleicher et al 2004). Even the Earth can be investigated as a transiting planet during lunar eclipse observations, when we can study the absorption lines of major atmospheric constituents such as CH 4 , H 2 O, O 2 , O 3 , and CO 2 in reflected light from the Sun by the Moon (see e.g., Pallé et al 2009;Vidal-Madjar et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Venus transit 2004: Illustrating the capability of exoplanet transmission spectroscopy

Hedelt¹,

Alonso²,

Brown³

et al. 2011

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The transit of Venus in 2004 offered the rare possibility to remotely sense a well-known planetary atmosphere using ground-based absorption spectroscopy. Transmission spectra of Venus' atmosphere were obtained in the near infrared using the Vacuum Tower Telescope (VTT) in Tenerife. Since the instrument was designed to measure the very bright photosphere of the Sun, extracting Venus' atmosphere was challenging. We were able to identify CO 2 absorption lines in the upper Venus atmosphere. Moreover, the relative abundance of the three most abundant CO 2 isotopologues could be determined. The observations resolved Venus' limb, showing Doppler-shifted absorption lines that are probably caused by high-altitude winds. We demonstrate the utility of groundbased measurements in analyzing the atmospheric constituents of a terrestrial planet atmosphere using methods that might be applied in future to terrestrial extrasolar planets.

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Detection of neutral sodium above Mercury during the transit on 2003 May 7

Cited by 75 publications

References 18 publications

Mercury exosphere I. Global circulation model of its sodium component

Mercury exosphere I. Global circulation model of its sodium component

Constraints on the exosphere of CoRoT-7b

Venus transit 2004: Illustrating the capability of exoplanet transmission spectroscopy

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