The dust trail complex of comet 79P/du Toit-Hartley and meteor outbursts at Mars

Abstract

Aims. Meteoroid trails ejected during past perihelion passages of the Mars-orbit-intersecting comet 79P/du Toit-Hartley have the potential of generating meteor outbursts in the Martian atmosphere. Depending on timing and intensity, the effects of these outbursts may be detectable by instrumentation operating in the vicinity of Mars. We aim to generate predictions for meteor activity in the martian atmosphere related to that comet; to search for evidence, in planetary mission data, that such activity took place; and to make predictions for potentially detectable future activity. Methods. We have modelled the stream by integrating numerically the states of particle ensembles, each ensemble representing a trail of meteoroids ejected from the comet during 39 perihelion passages from 1803, and propagated them forward in time, concentrating on those particles that physically approach Mars in the recent past and near future. Results. We find several instances where meteor outbursts of low to moderate intensity may have taken place at Mars since 1997. A search through Mars Global Surveyor (MGS) radio science data during two periods in 2003 and 2005 when data coverage was available showed that a plasma layer did indeed form in the martian ionosphere for a period of a few hours in April 2003 as a direct consequence of the predicted outburst. The apparent failure to identify such an event in 2005 could be due to those meteoroids ablating lower in the atmosphere or that the cometary dust follows a different particle size distribution than what was assumed. Our study highlights the need for further theoretical modelling of the response of the martian ionosphere to a time-variable meteoroid flux, observations of the comet itself and, most importantly, regular monitoring of the martian ionosphere during future outbursts predicted by our model.

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment

“…However, evidence that the properties of terrestrial meteoric layers vary during meteor showers is weak, despite predictions of significant variations [ Grebowsky et al , 1998; McNeil et al , 2001; Grebowsky and Aikin , 2002]. Withers et al (submitted manuscript, 2008) investigate the hypothesis that Martian meteoric layers are affected by meteor showers [ Christou et al , 2007; Withers et al , 2007]. The distribution of meteoric layers throughout the Mars year is shown in Figure 11 following calculations outlined in .…”

Solar rotation effects on the Martian ionosphere

“…M1 layer, occurs with its peak at~110 km altitude with a peak density (N m M1) of 10 9 m À3 . While the M2 layer occurs daily with a clear peak, the M1 layer is irregular and occurs sometimes with a peak, ledge, or shoulder [Bougher et al, 2001;Christou et al, 2007;Mendillo et al, 2006;Withers, 2009]. The M1 layer is formed by solar X-ray radiation at~1-20 nm wavelength and also by electron-impact ionization [Fox, 2004].…”

Numerical simulations of the ionosphere of Mars during a solar flare

“…The most distinctive observational feature of the M1 region is its variability [ Withers , 2009]. Its shape, width, peak electron density, and peak altitude all vary on time scales less than or equal to the 2 h interval between MGS radio occultation measurements [ Christou et al , 2007]. The immense variability of the Sun's soft X‐ray irradiance on this and shorter time scales [ Woods et al , 2005, and references therein] is an obvious contributor to this ionospheric variability.…”