Predictions of the effects of Mars's encounter with comet C/2013 A1 (Siding Spring) upon metal species in its ionosphere

Abstract

Citation:Withers, P. (2014) Abstract The infall of dust from the coma of comet C/2013 A1 (Siding Spring) and its subsequent ablation in the atmosphere of Mars has the potential to affect the abundances of metal species in the atmosphere and ionosphere. We develop relationships between properties of the dust population in the coma and densities of metal species in the atmosphere and ionosphere. These can be used to predict the abundances of metal species in the atmosphere and ionosphere during the encounter. Given postencounter observations of the atmosphere and ionosphere, they can also be used to infer relevant cometary properties. Although current predictions suggest that the influx of cometary dust will be comparable to the sporadic background, the higher entry speed involved, which leads to a greater production rate of ions during ablation, means that metal ion abundances may be enhanced during and after the encounter.

MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars

“…It remains to be seen whether this difference means that two distinct layers are present, whether the ionospheric layer is different at the times and places observed, or whether the two independent methods of detection are biased to yield somewhat different results. Similarly, the profiles derived here are comparable in density but higher in altitude to ionospheric profiles attributed to meteor ablation on Mars in the past [ Withers et al ., ] and predicted for Comet Siding Spring [ Withers , ].…”

“…Motivated by concerns over spacecraft safety, detailed modeling of cometary dust predicted relatively low risk of spacecraft damage from dust impacts [ Kelley et al ., ; Moorhead et al ., ; Vaubaillon et al ., ; Tricarico et al ., ]. The effect of dust on Mars was of particular interest for its potential ionospheric effects [ Withers , ], as prior observations of Mars' ionospheric structure identified transient layers attributed to meteor influx [ Withers et al ., ]. Cometary gas impact was also considered for its potential effects on Mars' upper atmosphere [ Yelle et al ., ].…”

Mars: a small terrestrial planet

“…Concerning the solar cycle, the relevant dataset in term of minimum temporal coverage is just being completed; therefore, many studies are expected from now on. Withers (2014) analyzed Mars Global Surveyor radio-occultation and Mars Express radar data and confirmed the expected trend that the ionospheric peak electron density increases smoothly with increasing solar activity represented by the F10.7 space weather proxy, named from the solar radio flux at 10.7 cm (2800 MHz). This trend is not obviously identified in the Mars Express radio-occultation data alone (Peter et al 2014).…”

“…That was the first time that any effects of cometary material penetrating into the Mars' atmosphere could be investigated. Predictions have been published by Yelle et al (2014), Withers (2014), and Gronoff et al (2014). A major effect was the deposition of metallic species in the upper atmosphere and the associated increase in ionization.…”

UV production of methane from surface and sedimenting IDPs on Mars in light of REMS data and with insights for TGO

“…Krasnopolsky et al, 2004;Formisano et al, 2004;Geminale et al, 2008;2011;Mumma et al, 2009) without concluding that all results are therefore suspect (Zahnle et al, 2011). kg (Schneider et al, 2015), than the largest of the Fries et al (2016) While it is possible that Siding Spring-derived materials have a larger ablated fraction as compared to typical meteoritic accretion due to increased velocity (Whithers, 2014), it seems unlikely that any of the hypothetical streams described by Fries et al (2016) Despite these challenges, the idea put forward by Fries et al (2016) of photolysis during atmospheric passage is worthy of consideration. If a large fraction of methane is deposited high in the atmosphere, the consumed organic carbon becomes unavailable to surface reservoirs, thereby reducing the equilibrium atmospheric value.…”