Dayside-to-nightside dust coma brightness asymmetry and its implications for nightside activity at Comet 67P/Churyumov–Gerasimenko

Gerig, Selina-Barbara; Pinzón-Rodríguez, O.; Marschall, Raphael; Wu, Jong-Shinn; Thomas, N.

doi:10.1016/j.icarus.2020.113968

Cited by 16 publications

(14 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of course, the Haser (1957) model, which assumes spherically symmetric outflow from a point source, is far too simplistic to be directly applied to data from Rosetta 67P/C-G. From Rosetta's vantage point embedded in the coma of 67P/C-G, the nucleus is clearly resolved and far from spherical (Figure 1), and observed gas (e.g., Migliorini et al 2016) and dust (e.g., Gerig et al 2018) outbursts are not axisymmetric. Thus, it is questionable whether the analytic prediction of Haser (1957, namely, N ∝ ρ −1 ) holds for Alice data.…”

Section: Discussionmentioning

confidence: 99%

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

Keeney

Stern

Feldman

et al. 2019

View full text Add to dashboard Cite

Following our previous detection of ubiquitous H 2 O and O 2 absorption against the far-UV continuum of stars located near the nucleus of Comet 67P/Churyumov-Gerasimenko, we present a serendipitously observed stellar occultation that occurred on 2015 September 13, approximately one month after the comet's perihelion passage. The occultation appears in two consecutive 10-minute spectral images obtained by Alice, Rosetta's ultraviolet (700-2100 Å) spectrograph, both of which show H 2 O absorption with column density > 10 17.5 cm −2 and significant O 2 absorption (O 2 /H 2 O ≈ 5-10%). Because the projected distance from the star to the nucleus changes between exposures, our ability to study the H 2 O column density profile near the nucleus (impact parameters < 1 km) is unmatched by our previous observations. We find that the H 2 O and O 2 column densities decrease with increasing impact parameter, in accordance with expectations, but the O 2 column decreases ∼ 3 times more quickly than H 2 O. When combined with previously published results from stellar appulses, we conclude that the O 2 and H 2 O column densities are highly correlated, and O 2 /H 2 O decreases with increasing H 2 O column.

show abstract

Section: Discussionmentioning

confidence: 99%

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

Keeney

Stern

Feldman

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In addition, evidence for particles falling back to the nucleus are several (Keller et al 2017). Models of the density distribution for a coma dominated by gravitationally bound particles on ballistic trajectories predict an excess of particles in the inner coma with respect to the density expected for free-radial outflow (Chamberlain & Hunten 1987;Gerig et al 2018). There are some hints of such a deviation from free-radial outflow in OSIRIS optical images (Gerig et al 2018), which would be amplified if the observed trend for a smaller albedo at smaller cometocentric distances is considered.…”

Section: Radial Variation Of the Bolometric Albedomentioning

confidence: 99%

“…Models of the density distribution for a coma dominated by gravitationally bound particles on ballistic trajectories predict an excess of particles in the inner coma with respect to the density expected for free-radial outflow (Chamberlain & Hunten 1987;Gerig et al 2018). There are some hints of such a deviation from free-radial outflow in OSIRIS optical images (Gerig et al 2018), which would be amplified if the observed trend for a smaller albedo at smaller cometocentric distances is considered. Deviations are also conspicuous for the dust thermal radiation measured in the microwave, which samples essentially large particles, and shows a steep decrease of the column density at impact parameters below 10 km (Schloerb et al 2017).…”

Section: Radial Variation Of the Bolometric Albedomentioning

confidence: 99%

VIRTIS-H observations of the dust coma of comet 67P/Churyumov-Gerasimenko: spectral properties and color temperature variability with phase and elevation

Bockelée‐Morvan

Leyrat

Erard

et al. 2019

A&A

View full text Add to dashboard Cite

We analyze 2-5 µm spectroscopic observations of the dust coma of comet 67P/Churyumov-Gerasimenko obtained with the VIRTIS-H instrument onboard Rosetta from 3 June to 29 October 2015 at heliocentric distances r h = 1.24-1.55 AU. The 2-2.5 µm color, bolometric albedo, and color temperature are measured using spectral fitting. Data obtained at α = 90 • solar phase angle show an increase of the bolometric albedo (0.05 to 0.14) with increasing altitude (0.5 to 8 km), accompanied by a possible marginal decrease of the color and color temperature. Possible explanations include the presence in the inner coma of dark particles on ballistic trajectories, and radial changes in particle composition. In the phase angle range 50-120 • , phase reddening is significant (0.031 %/100 nm/ • ), for a mean color of 2 %/100 nm at α = 90 • , that can be related to the roughness of the dust particles. Moreover, a decrease of the color temperature with decreasing phase angle is also observed at a rate of ∼ 0.3 K/ • , consistent with the presence of large porous particles, with low thermal inertia, and showing a significant day-to-night temperature contrast. Comparing data acquired at fixed phase angle (α = 90 • ), a 20% increase of the bolometric albedo is observed near perihelion. Heliocentric variations of the dust color are not significant in the analyzed time period. Measured color temperatures are varying from 260 to 320 K, and follow a r 0.6 h variation in the r h = 1.24-1.5 AU range, close to the expected r 0.5 h value.

show abstract

“…Rinaldi et al (2016) found that closer than 4 km from the surface the dust intensity decreases much faster than 1/ρ, which implies that the dust acceleration region is sampled by our measurements at 3.1 km from the comet centre. Gerig et al (2018) determined that the average starting point of the 1/ρ behaviour is (11.9 ± 2.8) km. Since we are not fulfilling the 'steady state' condition, the determined A f ρ cannot be directly compared with ground-based global measurements.…”

Section: Dust Brightness and A F ρmentioning

confidence: 99%

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Tubiana

Rinaldi

Güttler

et al. 2019

A&A

Self Cite

View full text Add to dashboard Cite

Context. On 27 April 2015, when 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving towards perihelion, the OSIRIS and VIRTIS-M instruments on board Rosetta simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the dust, H 2 O and CO 2 gas spatial distribution in the inner coma. To do this we performed a quantitative analysis of the release of dust and gas and compared the observed H 2 O production rate with the one calculated using a thermo-physical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H 2 O emission band) and 4200 nm (CO 2 emission band). We measured the average signal in a circular annulus, to study spatial variation around the comet, and in a sector of the annulus, to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet centre.Results. The spatial correlation between dust and water, both coming from the sun-lit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO 2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0 • sub-solar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO 2 production. An excess of measured water production, with respect to the value calculated using a simple thermo-physical model, is observed when the head lobe and regions of the Southern hemisphere with strong seasonal variations are illuminated (sub-solar longitude 270 • -50 • ). A drastic decrease in dust production, when the water production (both measured and from the model) displays a maximum, happens when typical Northern consolidated regions are illuminated and the Southern hemisphere regions with strong seasonal variations are instead in shadow (sub-solar longitude 50 • -90 • ). Possible explanations of these observations are presented and discussed.

show abstract

Dayside-to-nightside dust coma brightness asymmetry and its implications for nightside activity at Comet 67P/Churyumov–Gerasimenko

Cited by 16 publications

References 41 publications

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

VIRTIS-H observations of the dust coma of comet 67P/Churyumov-Gerasimenko: spectral properties and color temperature variability with phase and elevation

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Contact Info

Product

Resources

About