Probing of meteor showers at Mars during the encounter of comet C/2013 A1: predictions for the arrival of MAVEN/Mangalyaan
© Haider and Pandya. 2015
Received: 24 September 2014
Accepted: 17 April 2015
Published: 17 June 2015
We have estimated (1) production rates, (2) ion and electron densities of meteor ablation and (3) ionization for different masses and velocities of meteoroids when comet C/2013 A1 crossed the orbit of Mars on 19 October, 2014 at 18:27 UT. Meteor ablations of small masses < 10−4 g have created a broad layer between altitude ~ 90 km and 110 km. The meteoroids of large masses ≥ 10−4 g are burnt at around 60–90 km well below the main ionization peak at altitude ~160 km produced in the nighttime by solar wind particle impact. The production rates and densities of 15 metallic ions (Mg+, Fe+, Si+, MgO+, FeO+, SiO+, MgCO2 +, MgO2 +, FeCO2 +, FeO2 +, SiCO2 +, SiO2 +, MgN2 +, FeN2 +, and SiN2 +) have been computed self-consistently between altitudes 50 km and 150 km. The twelve major peaks in the Ion Mass Spectra (IMS) are predicted by our model calculations. Our predicted ion and electron density profiles of metals provide benchmark values that can be observed by plasma probes onboard Mars Express (MEX), Mars Atmosphere and Volatile Evolution (MAVEN) and Mangalyaan.
In this paper we have estimated production rates, ion and electron densities for meteor ionization of different masses and velocities of meteoroids at solar zenith angle (SZA) 110°. Our calculation suggests that two broad meteoric layers can be formed in the middle ionosphere during the encounter of the comet C/2013 A1 with the atmosphere of Mars. It is found that the meteor ablation of small masses < 10−4 g would occur between altitude 90 km and 110 km where the free molecular path is several orders larger than the meteoroid size. This is known as micrometeoroids . The meteoroids of large masses ≥ 10−4 g will penetrate deeper into the atmosphere and burn at altitude range 60 – 90 km. The predicted rate of ion formation and ion/electron density of meteors of all masses increases with velocities of meteoroids. During the meteor showers the ion and electron density are increased by several orders of magnitude in the middle ionosphere of Mars.
Earlier measurements of meteoric layers on mars
The presence of meteoric layers at about 80 km was first reported in the night time from the observations made by Mars 4 and Mars 5 . Later a meteor observing campaign was carried out by Panoramic camera (Pancam) onboard Mars Exploration Rover (MER) Spirit which detected two Martian showers on 18 November and 27 October 2005 when comet Halley and 2001/R1 LONEOS intersected the orbit of Mars from a close distance 0.067 AU and 0.001 AU, respectively. Domokos et al.  analyzed nighttime Pancam observations and estimated an upper limit of meteoroid flux 1.2× 10−19 cm−2 s−1 of mass larger than 4 g. Molina-Cuberos et al.  used micro sized meteoroid fluxes 10−19 to10−17 cm−2 s−1 for masses ~10−4 to 10−10 g and calculated maximum electron density ~2 × 104 cm−3 and 3 × 102 cm−3 during the daytime and nighttime ionosphere of Mars at altitudes 85 km and 83 km respectively.
Mars Global Surveyor (MGS) has observed 5600 electron density profiles from radio science experiment during the period 24 December 1998 to 9 June 2005 [9-11]. Withers et al.  found meteoric layers in 71 out of these 5600 electron density profiles. They have reported mean peak electron density (1.33 ± 0.5) × 104 cm−3 in the meteoric layer at a mean altitude of 91.7 ± 4.8 km. Their analysis suggests that the characteristics of these meteoric layers vary with season, SZA and latitude. Later Pandya and Haider  analyzed 1500 MGS electron density profiles to study the physical characteristics of meteoric plasma layers over Mars during the period January-June 2005. They found that 65 electron density profiles out of these 1500 profiles were strongly perturbed with peak densities ~ (0.5–1.4) × 104 cm−3 at altitudes between 80 km and 105 km, presumably due to ionization of meteoric atoms. Using these profiles they examined TEC in the lower ionosphere of Mars and found that maximum values of TEC occurred on 21 January and 23 May 2005, when comets 2007 PL42 and 4015 Wilson-Harrington intersected the orbit of Mars from close distances of 1.49 AU and 1.17 AU, respectively. The TEC values were increased by a factor of 5–7 on these days. Pandya and Haider  associated this significant increase with the meteor showers that were produced when Mars crossed the dust stream left along the orbits of these comets. These meteor showers were detected on Mars at different locations and at different times. The meteor shower of 21 January 2005 was observed at SZA = 74.3°, latitude 77.7°N and longitude 197.2°E during summer season (Ls = 147.4°). The meteor shower of 23 May 2005 was detected in the autumn season at Ls = 216.2°, SZA = 84.9°, latitude = 65.1°N and longitude 20.2°E.
Since 2004 MaRS experiment has observed 557 electron density profiles in the daytime and nighttime ionosphere of Mars [13,14]. Patzold et al.  observed meteoroid layers in 8% electron density profiles (i.e. 10 of 120 electron density profiles) of MEX measurements during the daytime ionosphere. Recently Haider et al.  have identified meteoric layers in two electron density profiles of MEX observations carried out in the nighttime ionosphere also, one on 22 August and the other on 25 September, 2005.
Modeling and input parameters
Our chemical model depends on the temperature and density of the atmosphere. The nighttime temperature and density of gases CO2, N2, O2, O and CO are calculated by Bougher et al.  between altitude 100 km and 220 km for the period September to October 2014. They solved 3-D MTGCM (Mars Thermosphere General Circulation Model) to study the atmosphere of Mars at different local time, latitude, longitude and seasons. We have taken temperature and density from this model for 19 October, 2014 at altitude from 100 km to 150 km. Between 50 km and 100 km, the temperature and density of Haider et al.  are used after scaling them for 19 October, 2014. The equations of motion, ablation and energy are solved [8, 15] to calculate the ion production rates due to impact of meteoroids with different masses in the nighttime ionosphere of Mars. We have assumed cometary meteoroids which are composed of 61.7% oxygen, 24.2% silicon, 8.2% magnesium, and 5.9% iron in atoms of element to the total . The ions Fe+, Mg+ and Si+ are produced due to meteor ablation in the nighttime ionosphere. The minimum velocities of Fe+, Mg+ and Si+ are taken 9.4, 11.1 and 11 km/s, respectively for the calculation of ionization probabilities. The rate coefficients of 57 chemical reactions given by Haider et al.  have been used to calculate electron density of metals. Using this chemical scheme we have predicted IMS and electron density in the nighttime ionosphere for different masses and velocities of meteoroids.
We have solved continuity coupled equations under steady state condition to predict IMS spectra. In this calculation transport of ions is neglected because transport time is several orders of magnitude higher than the chemical lifetime. In this model densities of each ion species, ni +, and electron, ne, are calculated from the continuity equation and the charge neutrality condition using P i - l i n i + = 0 and n e - ∑ n i + = 0, where P i is the production rate by meteoroids/micrometeoroids and ion molecule reactions, and l i is the specific loss due to ion-molecule reactions and recombination with electrons. We have also investigated densities of metallic clusters due to termolecular associations of metallic ions with neutral molecules. It should be noted that direct meteoric ionization is the only ionization source considered here. The ionization by solar radiation or photoelectrons at the peak altitude of the meteoroid/micrometeoroid ablation is low and its influence on the concentration of electrons and metallic ions is approximately negligible.
Results and discussion
Peak height and peak electron densities due to micrometeoroids and meteoroids ablation at different velocities
Velocity 10 km/s
Velocity 18 km/s
Velocity 30 km/s
Peak height (km)
Peak electron density(cm −3 )
Peak height (km)
Peak electron density(cm −3 )
Peak height (km)
Peak electron density(cm −3 )
~1.0 x 104
~3.5 x 105
~3.0 x 107
~1.0 x 101
~6.0 x 102
~5.0 x 104
Recently, radio occultation experiment onboard MGS and MEX has observed meteoric plasma layers in the daytime and nighttime ionosphere of Mars at altitude range 80–100 km with peak electron density ~ 103-104 cm−3 [cf. [13-15]]. The density of meteoric layers can change with the intensity of meteor showers. We report that the predicted peak electron densities due to incoming micrometeoroids of velocities 18 km/s and 30 km/s are larger than MGS/MEX measurements by ~ 2–3 orders of magnitude. This suggests that the intensity of proposed meteor showers would be significantly large on 19 October, 2014 due to ablation of micrometeoroids of high velocity. Thus, high speed micrometeoroids will produce bright showers in the atmosphere of Mars. The calculated peak electron densities for incoming meteoroids of velocities 10 km/s and 18 km/s are lower than MGS/MEX measurements by ~ 2–3 orders of magnitude. The maximum electron densities predicted due to ablation of micrometeoroids and meteoroids of velocities 10 km/s and 30 km/s respectively are comparable in magnitude with these measurements.
Initially ions Mg+, Fe+ and Si+ are produced by direct meteoric ionization. The major cluster ions FeCO2 + and SiCO2 + are produced due to associations of Fe+ and Si+ with CO2 by three body reactions. The other major cluster ion MgN2 + is also produced by three body reaction due to attachment of Mg+ with N2. These cluster ions were lost by dissociative recombination reactions. The ions FeCO2 + and SiCO2 + are also produced from termolecular associations of Fe+ and Si+ with CO2 respectively at the rate coefficient 1.0 × 10−30 cm6 s−1 . The ions MgCO2 +, MgO2 + and MgN2 + are formed due to associations of CO2, O2, and N2 with Mg+ at rate constants 1.0 × 10−30, 9.0 × 10−30(200/T) and 1.0 × 10−30 cm6 s−1 respectively [25-27]. The dissociative recombination rate coefficients of clusters were estimated to be ~107 cm3 s−1 [24,27,28], which is four orders of magnitude higher than the metallic ion recombination coefficient ~10−12 cm3 s−1 [cf. [24,29]]. The ions FeO+, SiO+ and MgO+ are formed due to loss of Fe+, Si+ and Mg+ with O3 respectively. The densities of FeO+, SiO+ and MgO+ are lower than the densities of FeCO2 +, SiCO2 + and MgCO2 + respectively because the densities of O3 is lower than CO2. In the meteoric layer of earth’s ionosphere, termolecular reactions of metallic ions with oxygen followed by molecular dissociative recombination are very efficient processes. In the Mars atmosphere the concentration of oxygen is not high enough to decrease the concentration of metal ions through this reaction.
Ion masses corresponding to ≤100 amu
Fe+ , MgO2 + , SiN2 +
FeO+, SiCO2 +
Uncertainty in the model
Our model depends on the neutral density, temperature, meteoroid flux and various chemical reactions. The neutral density and temperature are taken from Bougher et al.  for 19 October, 2014, when comet C/2013 A1 crossed the orbit of Mars. The meteoroid fluxes are not measured in the orbit of Mars. We do not know how much meteoroid flux will precipitate in the Martian ionosphere during ablation on 19 October, 2014. We have taken meteoroid fluxes from the measurements made by Pioneers 8/11 and Helios satellites in the orbit of earth with their experimental uncertainties of 15-20% . These fluxes were scaled to Mars orbit. Some changes ~ 5–8% are expected in the ion and electron density due to this uncertainty in the model. However, scaled spectra of meteoroids are in good agreement with the upper limit of meteoroid flux measured by MER cameras for mass larger than 4 g at Mars. The present chemical model is developed by a sequence of algebraic expressions, which obtains solutions after sufficient iterations for ion and electron density. Transport effect of ions and electrons are omitted in this model because this effect is appreciable above 200 km only. We note that above uncertainties are not very large.
Constraints on the meteor measurements from MAVEN and mangalyaan
Hubble Space Telescope observations indicated that the bulk of grains produced by comet C/2013 A1 will miss Mars. Only few percent of grains of higher velocities will reach Mars, peaking approximately 90–100 minutes after the close approach . Later Tricarico et al.  confirmed that younger grains of sub millimeter to several millimeters can reach Mars at higher velocities. Based on model results of Kelley et al.  MAVEN, MEX and Mangalyaan were impacted by large dust grains and Mars received as many as ~ 107 grains (100 kg of total dust). The radio occultation experiment onboard MGS and MEX have observed meteoric plasma layers in most of the electron density profiles during daytime and nighttime ionosphere of Mars [cf. [2,11,15]]. MGS has now stopped working since 2 November, 2006, but MEX is orbiting around Mars. However, MEX could not measure meteor electron density from this experiment on 19 October, 2014 during the encounters of comet C/2013 A1 with the atmosphere of Mars.
MAVEN and Mangalyaan are performing measurements from a highly elliptical orbit with a minimum height at about 150 km and 372 km respectively (www.isro.org/mars/updates.aspx; www.nasa.gov/mission_pages/maven/main/). These missions did not carry radio occultation experiment, which can measure complete electron density profiles above 50 km. MAVEN carries Langmuir probe and ion/neutral mass spectrometer experiments. Mangalyaan also carries a mass spectrometer. Both experiments can measure plasma density in the upper atmosphere and exosphere of Mars. We have estimated meteoric ion and electron densities between altitude 50 km and 150 km for 19 October, 2014 due to intersection of comet C/2013 A1 with the atmosphere of Mars. The mass spectrometer onboard MAVEN is designed to measure ion concentrations as low as 0.1 cm−3 (www.nasa.gov/mission_pages/maven/main/). Using this instrument the meteor density is investigated for eight ions (i.e. Mg, Fe, Na, K, Mn, Ni, Cr and Zn) between masses 24 and 100 amu. Mangalyaan also carries a high resolution color camera operating in the visible range (0.4 μ–0.7 μ). This camera is measuring high quality visible images of Mars and its environments. The velocity of Mangalyaan at perigee (~372 km) is about 4 km/s where as it is less than 10 m/s at apogee (~80000 km) (www.isro.org/mars/updates.aspx). Thus, this mission allows imaging of localized scenes at higher spatial resolution as well as provides a synoptic view of the full globe during its elliptical orbit. Therefore, the light of meteor bombardments during occurrence of meteor shower on 19 October, 2014 can be detected from this color camera. The analysis of this data is under progress.
We have predicted two broad meteoric layers in the nighttime ionosphere of Mars at altitude range 90–110 km and 60–90 km due to ablation of micrometeoroids and meteoroids respectively, when comet C/2013 A1 crossed the orbit of Mars on 19 October, 2014. The mass densities of 15 metallic ions are also predicted in the vicinity of ionization peaks. These ions are produced by direct meteoric ionization and lost by dissociative recombination. The production rates are calculated using the equations of motion, ablation, and energy. The ion mass densities are estimated by coupled continuity equations controlled by steady state condition. The magnitude of the meteoric layers depends on the concentration of metals and incoming velocities, viz., 10 km/s, 18 km/s and 30 km/s of meteoroids and micrometeoroids, We have obtained that the concentrations of ions and electron strongly depend on the variations of the incoming velocities. It is also found that ion and electron densities can be increased by several orders of magnitude in the middle ionosphere of Mars during the meteor showers. Our estimated results can be confirmed in future by plasma probes onboard MAVEN and Mangalyaan.
Authors are thankful to MAVEN and Mangalyaan team for the discussion on Mars-comet tail intersection on 19 October, 2014 when meteor shower events can be detected by these missions. We also thank S.W. Bougher (email: firstname.lastname@example.org) for providing us density and temperature data obtained from Mars Thermosphere General Circulation Model (MTGCM) of Mars atmosphere for the month of October, 2014.
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