Comment on “A cometary origin for atmospheric martian methane” by Fries et al., 2016
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Comment
Reports of transient plumes of martian atmospheric methane (Mumma et al., 2009
Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T., Bonev, B.P., DiSanti, M.A., Mandell, A.M., Smith, M.D. (2009) Strong release of methane on Mars in northern summer 2003. Science 323, 1041–1045.
; Webster et al., 2015Webster, C.R., Mahaffy, P.R., Atreya, S.K., Flesch, G.J., Mischna, M.A., Meslin, P.-Y., Farley, K.A., Conrad, P.G., Christensen, L.E., Pavlov, A.A., Martin-Torres, J., Zorzano, M.-P., McConnochie, T.H., Owen, T., Eigenbrode, J.L., Glavin, D.P., Steele, A., Malespin, C.A., Archer Jr., P.D., Sutter, B., Coll, P., Frissinet, C., McKay, C.P., Moores, J.E., Schwenzer, S.P., Bridges, J.C., Navarro-Gonzalez, R., Gellert, R., Lemmon, M.T., the MSL Science Team (2015) Mars methane detection and variability at Gale crater. Science 347, 415–417.
) have led to suggestions of biologic or abiotic surface sources. Schuerger et al. (2012)Schuerger, A.C., Moores, J.E., Clausen, C.A., Barlow, N.G., Britt, D.T. (2012) Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions. Journal of Geophysical Research: Planets (1991–2012), 117(E8).
examined the production of methane near the surface from interplanetary dust particles. They found this mechanism was capable of yielding the background value of methane, but could not reproduce plume densities by bolide, airburst or other meteor impact process. Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
draw on the work of Schuerger et al. (2012)Schuerger, A.C., Moores, J.E., Clausen, C.A., Barlow, N.G., Britt, D.T. (2012) Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions. Journal of Geophysical Research: Planets (1991–2012), 117(E8).
and propose that the methane plumes are sourced instead from intense meteor showers with conversion at high altitudes.The Fries et al. (2016)
Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
methane (CH4) production mechanism creates a scaling relationship between meteor shower deposition and plume mass, giving 8 x 108 and 2 x 108 kg of meteoric material for the plumes of 45 and 10 ppbv of CH4, respectively (Mumma et al., 2009Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T., Bonev, B.P., DiSanti, M.A., Mandell, A.M., Smith, M.D. (2009) Strong release of methane on Mars in northern summer 2003. Science 323, 1041–1045.
; Webster et al., 2015Webster, C.R., Mahaffy, P.R., Atreya, S.K., Flesch, G.J., Mischna, M.A., Meslin, P.-Y., Farley, K.A., Conrad, P.G., Christensen, L.E., Pavlov, A.A., Martin-Torres, J., Zorzano, M.-P., McConnochie, T.H., Owen, T., Eigenbrode, J.L., Glavin, D.P., Steele, A., Malespin, C.A., Archer Jr., P.D., Sutter, B., Coll, P., Frissinet, C., McKay, C.P., Moores, J.E., Schwenzer, S.P., Bridges, J.C., Navarro-Gonzalez, R., Gellert, R., Lemmon, M.T., the MSL Science Team (2015) Mars methane detection and variability at Gale crater. Science 347, 415–417.
). While Zahnle et al. (2011)Zahnle, K., Freedman, R.S., Catling, D.C. (2011) Is there methane on Mars? Icarus 212, 493–503.
indicated that these values overestimate the abundance of CH4 by an order of magnitude, we show that even the lowest value (2 x 107 kg for the 10 ppbv plume) is in excess of any observed or predicted fluences by several orders of magnitude.First, we compare the Fries et al. (2016)
Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
values to the global flux of interplanetary dust particles on Earth, which is estimated to be between 5 x 103 and 3 x 105 kg/day (Plane, 2012Plane, J. (2012) Cosmic dust in the earth’s atmosphere. Chemical Society Reviews 41, 6507–6518.
). The fluence of meteoric material at Earth is not strongly increased by meteor showers (Grebowsky et al., 1998Grebowsky, J.M., Goldberg, R.A., Pesnell, W.D. (1998) Do meteor showers significantly perturb the ionosphere? Journal of Atmospheric and Solar-Terrestrial Physics 60, 607–615.
) and this is indicative that meteor showers do not in general deliver significantly more material than the sporadic background. As Mars has three times less surface area, Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
therefore requires a normal meteor shower to deliver 180 times more material than the upper limit of Earth’s total daily fluence. Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
suggest that Comet C/2007 H2 Skiff’s meteor shower is correlated with a high-altitude dust plume (Sánchez-Lavega et al., 2015Sánchez-Lavega, A., García Muñoz, A., García-Melendo, E., Pérez-Hoyos, S., Gómez-Forrellad, J.M., Pellier, C., Delcroix, M., López-Valverde, M. A., González-Galindo, F., Jaeschke,W., Parker, D., Phillips, J., Peach, D. (2015) An extremely high-altitude plume seen at Mars’ morning terminator. Nature 518, 525-528.
), although there can be no constraint on CH4 as no measurements were made at the time. Model predictions of Skiff’s meteor shower do not provide a fluence or particle size, as these quantities are unconstrained by previous observations. Moreover, Skiff is unlikely to be able to deliver 2 x 107 kg/day as recent work (Crismani et al., 2016Crismani, M., Schneider, N., Jain, S., Plane, J., Carrillo-Sanchez, J., Deighan, J., Stevens, M., Evans, S., Chaffin, M., Stewart, I., Jakosky, B. (2016) Meteoric Metal Layer in Mars’ Atmosphere: Steady-state Flux and Meteor Showers. 47th Lunar and Planetary Sciences Conference, 2791.
) has shown that its fluence cannot exceed 103 kg/day.Next, we compare the Fries et al. (2016)
Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
values to the observed mass fluence during the close encounter of comet C/2014 A1 (Siding Spring), determined to be ~1.6 x 104 kg over the planet (Schneider et al., 2015Schneider, N.M., Deighan, J.I., Stewart, A.I.F., McClintock, W.E., Jain, S.K., Chaffin, M.S., Stiepen, A., Crismani, M., Plane, J.M.C., Carrillo-Sánchez, J.D., Evans, J.S., Stevens, M.H., Yelle, R.V., Clarke, J.T., Holsclaw, G.M., Montmessin, F., Jakosky, B.M. (2015) MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars. Geophysical Research Letters 42, 4755–4761.
). Comet Siding Spring’s dust stream was likely atypically dense, as the nucleus passed within 1.4 x 105 km of Mars, and Mars subsequently passed through the comet’s relatively fresh debris stream. (Note that Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
mention the comet Siding Spring case in the supplementary material, but do not use the observed fluence of Schneider et al. (2015)Schneider, N.M., Deighan, J.I., Stewart, A.I.F., McClintock, W.E., Jain, S.K., Chaffin, M.S., Stiepen, A., Crismani, M., Plane, J.M.C., Carrillo-Sánchez, J.D., Evans, J.S., Stevens, M.H., Yelle, R.V., Clarke, J.T., Holsclaw, G.M., Montmessin, F., Jakosky, B.M. (2015) MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars. Geophysical Research Letters 42, 4755–4761.
or full particle size distribution (Kelley et al., 2014Kelley, M.S., Farnham, T.L., Bodewits, D., Tricarico, P., Farnocchia, D. (2014) A Study of Dust and Gas at Mars from Comet C/2013 A1 (Siding Spring). The Astrophysical Journal Letters 792, L16.
)). Therefore, the fluence of the largest observed meteor shower at any planet was still three orders of magnitude less than necessary to explain any CH4 plume by the method of Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
.Finally, we consider other observational consequences of a meteoric deposition of 107 kg. This amount of material entering the atmosphere of Mars at relative orbital velocity (35 km/s for comet Skiff) would carry an equivalent energy of 6 x 1015 J. Using a model of cometary deposition derived from Yelle et al. (2014)
Yelle, R.V., Mahieux, A., Morrison, S., Vuitton, V., Hörst, S.M. (2014) Perturbation of the Mars atmosphere by the near-collision with Comet C/2013 A1 (Siding Spring). Icarus 237, 202–210.
, we create a scaling between meteoric deposition and thermospheric temperature increase and find, to first order, that a deposition of 107 kg would increase the thermosphere by 3 x 103 K. Therefore meteoric deposition of the required magnitude of Fries et al. (2016)Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
has readily observable consequences in the form of increased spacecraft drag (Zurek et al., 2015Zurek, R.W., Tolson, R.H., Baird, D., Johnson, M.Z., Bougher, S.W. (2015) Application of MAVEN accelerometer and attitude control data to Mars atmospheric characterization. Space Science Reviews 195, 30
) and enhanced thermospheric emissions (Jain et al., 2015Jain, S.K., Stewart, A.I.F., Schneider, N.M., Deighan, J., Stiepen, A., Evans, J.S., Stevens, M.H., Chaffin, M.S., Crismani, M., McClintock, W.E., Clarke, J.T., Holsclaw, G.M., Lo, D.Y., Lefèvre, F., Montmessin, F., Thiemann, E.M.B., Eparvier, F., Jakosky, B.M. (2015) The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations. Geophysical Research Letters 42, 9023–9030.
), neither of which have been observed at the time of meteor showers.Editor: Eric Oelkers
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References
Crismani, M., Schneider, N., Jain, S., Plane, J., Carrillo-Sanchez, J., Deighan, J., Stevens, M., Evans, S., Chaffin, M., Stewart, I., Jakosky, B. (2016) Meteoric Metal Layer in Mars’ Atmosphere: Steady-state Flux and Meteor Showers. 47th Lunar and Planetary Sciences Conference, 2791.
Show in context Moreover, Skiff is unlikely to be able to deliver 2 x 107 kg/day as recent work (Crismani et al., 2016) has shown that its fluence cannot exceed 103 kg/day.
View in article
Fries, M., Christou, A., Archer, D., Conrad, P., Cooke, W., Eigenbrode, J., ten Kate, I.L., Matney, M., Niles, P., Sykes, M., Steele, A., Treiman, A. (2016) A cometary origin for martian atmospheric methane. Geochemical Perspectives Letters 2, 10–23.
Show in context Fries et al. (2016) draw on the work of Schuerger et al. (2012) and propose that the methane plumes are sourced instead from intense meteor showers with conversion at high altitudes.
View in article
The Fries et al. (2016) methane (CH4) production mechanism creates a scaling relationship between meteor shower deposition and plume mass, giving 8 x 108 and 2 x 108 kg of meteoric material for the plumes of 45 and 10 ppbv of CH4, respectively (Mumma et al., 2009; Webster et al., 2015).
View in article
First, we compare the Fries et al. (2016) values to the global flux of interplanetary dust particles on Earth, which is estimated to be between 5 x 103 and 3 x 105 kg/day (Plane, 2012).
View in article
As Mars has three times less surface area, Fries et al. (2016) therefore requires a normal meteor shower to deliver 180 times more material than the upper limit of Earth’s total daily fluence.
View in article
Fries et al. (2016) suggest that Comet C/2007 H2 Skiff’s meteor shower is correlated with a high-altitude dust plume (Sánchez-Lavega et al., 2015), although there can be no constraint on CH4 as no measurements were made at the time.
View in article
Next, we compare the Fries et al. (2016) values to the observed mass fluence during the close encounter of comet C/2014 A1 (Siding Spring), determined to be ~1.6 x 104 kg over the planet (Schneider et al., 2015).
View in article
(Note that Fries et al. (2016) mention the comet Siding Spring case in the supplementary material, but do not use the observed fluence of Schneider et al. (2015) or full particle size distribution (Kelley et al., 2014)).
View in article
Therefore, the fluence of the largest observed meteor shower at any planet was still three orders of magnitude less than necessary to explain any CH4 plume by the method of Fries et al. (2016).
View in article
Therefore meteoric deposition of the required magnitude of Fries et al. (2016) has readily observable consequences in the form of increased spacecraft drag (Zurek et al., 2015) and enhanced thermospheric emissions (Jain et al., 2015), neither of which have been observed at the time of meteor showers.
View in article
Grebowsky, J.M., Goldberg, R.A., Pesnell, W.D. (1998) Do meteor showers significantly perturb the ionosphere? Journal of Atmospheric and Solar-Terrestrial Physics 60, 607–615.
Show in context The fluence of meteoric material at Earth is not strongly increased by meteor showers (Grebowsky et al., 1998) and this is indicative that meteor showers do not in general deliver significantly more material than the sporadic background.
View in article
Jain, S.K., Stewart, A.I.F., Schneider, N.M., Deighan, J., Stiepen, A., Evans, J.S., Stevens, M.H., Chaffin, M.S., Crismani, M., McClintock, W.E., Clarke, J.T., Holsclaw, G.M., Lo, D.Y., Lefèvre, F., Montmessin, F., Thiemann, E.M.B., Eparvier, F., Jakosky, B.M. (2015) The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations. Geophysical Research Letters 42, 9023–9030.
Show in context Therefore meteoric deposition of the required magnitude of Fries et al. (2016) has readily observable consequences in the form of increased spacecraft drag (Zurek et al., 2015) and enhanced thermospheric emissions (Jain et al., 2015), neither of which have been observed at the time of meteor showers.
View in article
Kelley, M.S., Farnham, T.L., Bodewits, D., Tricarico, P., Farnocchia, D. (2014) A Study of Dust and Gas at Mars from Comet C/2013 A1 (Siding Spring). The Astrophysical Journal Letters 792, L16.
Show in context (Note that Fries et al. (2016) mention the comet Siding Spring case in the supplementary material, but do not use the observed fluence of Schneider et al. (2015) or full particle size distribution (Kelley et al., 2014)).
View in article
Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T., Bonev, B.P., DiSanti, M.A., Mandell, A.M., Smith, M.D. (2009) Strong release of methane on Mars in northern summer 2003. Science 323, 1041–1045.
Show in context Reports of transient plumes of martian atmospheric methane (Mumma et al., 2009; Webster et al., 2015) have led to suggestions of biologic or abiotic surface sources.
View in article
The Fries et al. (2016) methane (CH4) production mechanism creates a scaling relationship between meteor shower deposition and plume mass, giving 8 x 108 and 2 x 108 kg of meteoric material for the plumes of 45 and 10 ppbv of CH4, respectively (Mumma et al., 2009; Webster et al., 2015).
View in article
Plane, J. (2012) Cosmic dust in the earth’s atmosphere. Chemical Society Reviews 41, 6507–6518.
Show in context First, we compare the Fries et al. (2016) values to the global flux of interplanetary dust particles on Earth, which is estimated to be between 5 x 103 and 3 x 105 kg/day (Plane, 2012).
View in article
Sánchez-Lavega, A., García Muñoz, A., García-Melendo, E., Pérez-Hoyos, S., Gómez-Forrellad, J.M., Pellier, C., Delcroix, M., López-Valverde, M. A., González-Galindo, F., Jaeschke,W., Parker, D., Phillips, J., Peach, D. (2015) An extremely high-altitude plume seen at Mars’ morning terminator. Nature 518, 525-528.
Show in context Fries et al. (2016) suggest that Comet C/2007 H2 Skiff’s meteor shower is correlated with a high-altitude dust plume (Sánchez-Lavega et al., 2015), although there can be no constraint on CH4 as no measurements were made at the time.
View in article
Schneider, N.M., Deighan, J.I., Stewart, A.I.F., McClintock, W.E., Jain, S.K., Chaffin, M.S., Stiepen, A., Crismani, M., Plane, J.M.C., Carrillo-Sánchez, J.D., Evans, J.S., Stevens, M.H., Yelle, R.V., Clarke, J.T., Holsclaw, G.M., Montmessin, F., Jakosky, B.M. (2015) MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars. Geophysical Research Letters 42, 4755–4761.
Show in context Next, we compare the Fries et al. (2016) values to the observed mass fluence during the close encounter of comet C/2014 A1 (Siding Spring), determined to be ~1.6 x 104 kg over the planet (Schneider et al., 2015).
View in article
(Note that Fries et al. (2016) mention the comet Siding Spring case in the supplementary material, but do not use the observed fluence of Schneider et al. (2015) or full particle size distribution (Kelley et al., 2014)).
View in article
Schuerger, A.C., Moores, J.E., Clausen, C.A., Barlow, N.G., Britt, D.T. (2012) Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions. Journal of Geophysical Research: Planets (1991–2012), 117(E8).
Show in context Schuerger et al. (2012) examined the production of methane near the surface from interplanetary dust particles.
View in article
Fries et al. (2016) draw on the work of Schuerger et al. (2012) and propose that the methane plumes are sourced instead from intense meteor showers with conversion at high altitudes.
View in article
Webster, C.R., Mahaffy, P.R., Atreya, S.K., Flesch, G.J., Mischna, M.A., Meslin, P.-Y., Farley, K.A., Conrad, P.G., Christensen, L.E., Pavlov, A.A., Martin-Torres, J., Zorzano, M.-P., McConnochie, T.H., Owen, T., Eigenbrode, J.L., Glavin, D.P., Steele, A., Malespin, C.A., Archer Jr., P.D., Sutter, B., Coll, P., Frissinet, C., McKay, C.P., Moores, J.E., Schwenzer, S.P., Bridges, J.C., Navarro-Gonzalez, R., Gellert, R., Lemmon, M.T., the MSL Science Team (2015) Mars methane detection and variability at Gale crater. Science 347, 415–417.
Show in context Reports of transient plumes of martian atmospheric methane (Mumma et al., 2009; Webster et al., 2015) have led to suggestions of biologic or abiotic surface sources.
View in article
The Fries et al. (2016) methane (CH4) production mechanism creates a scaling relationship between meteor shower deposition and plume mass, giving 8 x 108 and 2 x 108 kg of meteoric material for the plumes of 45 and 10 ppbv of CH4, respectively (Mumma et al., 2009; Webster et al., 2015).
View in article
Yelle, R.V., Mahieux, A., Morrison, S., Vuitton, V., Hörst, S.M. (2014) Perturbation of the Mars atmosphere by the near-collision with Comet C/2013 A1 (Siding Spring). Icarus 237, 202–210.
Show in context Using a model of cometary deposition derived from Yelle et al. (2014), we create a scaling between meteoric deposition and thermospheric temperature increase and find, to first order, that a deposition of 107 kg would increase the thermosphere by 3 x 103 K.
View in article
Zahnle, K., Freedman, R.S., Catling, D.C. (2011) Is there methane on Mars? Icarus 212, 493–503.
Show in context While Zahnle et al. (2011) indicated that these values overestimate the abundance of CH4 by an order of magnitude, we show that even the lowest value (2 x 107 kg for the 10 ppbv plume) is in excess of any observed or predicted fluences by several orders of magnitude.
View in article
Zurek, R.W., Tolson, R.H., Baird, D., Johnson, M.Z., Bougher, S.W. (2015) Application of MAVEN accelerometer and attitude control data to Mars atmospheric characterization. Space Science Reviews 195, 30
Show in context Therefore meteoric deposition of the required magnitude of Fries et al. (2016) has readily observable consequences in the form of increased spacecraft drag (Zurek et al., 2015) and enhanced thermospheric emissions (Jain et al., 2015), neither of which have been observed at the time of meteor showers.
View in article