09:37 〜 10:00
[PPS02-03] In-situ investigations of Martian regolith using seismic and acoustic measurements
★Invited Papers
キーワード：regolith, dust, seismology, microphone, atmosphere, surface
Regolith is ubiquitous in the Solar System covering all planetary surfaces. This material provides information about the past and on-going evolution of planetary surfaces and is also important to understand for space missions involving surface-interactions. In this talk we will discuss some novel in-situ techniques that have recently been applied to study Martian regolith material.
The NASA InSight mission [1] landed on Mars in November 2018 carrying, among other payloads, a robotic arm [2], a high-performance barometer [3], and the highly sensitive low-noise seismometer SEIS [4]. The first two approaches to studying planetary surface properties that we will discuss here exploit the fact that an elastic planetary surface deforms and tilts when a force is applied upon it. Such ground tilts are observable on the horizontal component of a seismometer. First, we explain how the ground tilt generated during the passage of convective vortices can be used to constrain the average elastic properties of the Martian sub-surface, as long as there are simultaneous atmospheric pressure and seismic measurements [5]. By studying almost 500 vortices, we estimate that the mean value of η (η = E/[1 − ν2], where E is the Young's modulus and ν is the Poisson's ratio) of the Martian ground in the region around InSight is 239 +/- 140 MPa from seismic and pressure data filtered in the 0.02 – 0.3 Hz frequency band. Our analyses are sensitive to ground properties to a depth of several meters to several tens of meters, and these average elastic properties are similar to those found in studies made with alternative techniques [6-8]. Then, we discuss a complementary experiment that pressed on the Martian ground using the scoop on the InSight robotic arm, thus generating a ground tilt that was measured by SEIS [9]. A quasi-static surface deformation approach [10] can then be used to retrieve the mean elastic parameters of the ground between the scoop and the SEIS instrument.
Next, we will move to the NASA Mars 2020 Perseverance mission [11] that landed on Mars in February 2020. The rover carries the SuperCam microphone [12,13] that records air pressure fluctuations during 167 s periods with a sampling rate of 25,000 samples per second at the height of about 2.1 m above the Martian surface. The SuperCam microphone provided the first in-situ recordings of sound from the Martian surface [14]. Recently, however, this microphone has also recorded the acoustic signals of grain impacts during an encounter with a dust-laden convective vortex (a dust devil). By analysing these acoustic signals, we have been able to provide the first in-situ quantification about the number density of particles in a Martian dust devil [15]. These data demonstrate the potential of acoustic measurements for improving our understanding of dust lifting and atmospheric transport on Mars. Such information is key for accurate simulation of the dust cycle and for the prediction of dust storms, in addition to being important for future space exploration as grain impacts are implicated in the degradation of hardware on the surface of Mars.
References: [1] Banerdt, W. B., et al. (2020). Nat. Geo., 13(3), 183-189. [2] Trebi-Ollennu, A., et al. (2018). SSR, 214(93). [3] Banfield, D., et al. (2019). SSR, 215(1), 4. [4] Lognonné, P., et al. (2019). SSR, 215(1), 12. [5] Murdoch, N., et al. (2021). JGR: Planets, 126, e2020JE006410. [6] Garcia, R.F., et al. (2020), JGR: Planets, 125(7), e2019JE006278 [7] Kenda, B., et al., (2020), JGR: Planets, 125(6), e2020JE006387. [8] Lognonné, P., et al. (2020). Nat. Geo., 13, 213-220. [9] Golombek, M. et al., Submitted to SSR. [10] Murdoch, N., et al. (2017). SSR, 211, 429-455. [11] Farley, K. A., et al. (2020). SSR, 216, 1-41. [12] Mimoun, D., et al. (2023). SSR, 219(1), 5. [13] Maurice, S., et al. (2021). SSR, 217, 1-108. [14] Maurice, S. et al. (2022) Nature 605, 653-658. [15] Murdoch, N. et al., (2022) Nat. Comm., 13(1), 7505.
The NASA InSight mission [1] landed on Mars in November 2018 carrying, among other payloads, a robotic arm [2], a high-performance barometer [3], and the highly sensitive low-noise seismometer SEIS [4]. The first two approaches to studying planetary surface properties that we will discuss here exploit the fact that an elastic planetary surface deforms and tilts when a force is applied upon it. Such ground tilts are observable on the horizontal component of a seismometer. First, we explain how the ground tilt generated during the passage of convective vortices can be used to constrain the average elastic properties of the Martian sub-surface, as long as there are simultaneous atmospheric pressure and seismic measurements [5]. By studying almost 500 vortices, we estimate that the mean value of η (η = E/[1 − ν2], where E is the Young's modulus and ν is the Poisson's ratio) of the Martian ground in the region around InSight is 239 +/- 140 MPa from seismic and pressure data filtered in the 0.02 – 0.3 Hz frequency band. Our analyses are sensitive to ground properties to a depth of several meters to several tens of meters, and these average elastic properties are similar to those found in studies made with alternative techniques [6-8]. Then, we discuss a complementary experiment that pressed on the Martian ground using the scoop on the InSight robotic arm, thus generating a ground tilt that was measured by SEIS [9]. A quasi-static surface deformation approach [10] can then be used to retrieve the mean elastic parameters of the ground between the scoop and the SEIS instrument.
Next, we will move to the NASA Mars 2020 Perseverance mission [11] that landed on Mars in February 2020. The rover carries the SuperCam microphone [12,13] that records air pressure fluctuations during 167 s periods with a sampling rate of 25,000 samples per second at the height of about 2.1 m above the Martian surface. The SuperCam microphone provided the first in-situ recordings of sound from the Martian surface [14]. Recently, however, this microphone has also recorded the acoustic signals of grain impacts during an encounter with a dust-laden convective vortex (a dust devil). By analysing these acoustic signals, we have been able to provide the first in-situ quantification about the number density of particles in a Martian dust devil [15]. These data demonstrate the potential of acoustic measurements for improving our understanding of dust lifting and atmospheric transport on Mars. Such information is key for accurate simulation of the dust cycle and for the prediction of dust storms, in addition to being important for future space exploration as grain impacts are implicated in the degradation of hardware on the surface of Mars.
References: [1] Banerdt, W. B., et al. (2020). Nat. Geo., 13(3), 183-189. [2] Trebi-Ollennu, A., et al. (2018). SSR, 214(93). [3] Banfield, D., et al. (2019). SSR, 215(1), 4. [4] Lognonné, P., et al. (2019). SSR, 215(1), 12. [5] Murdoch, N., et al. (2021). JGR: Planets, 126, e2020JE006410. [6] Garcia, R.F., et al. (2020), JGR: Planets, 125(7), e2019JE006278 [7] Kenda, B., et al., (2020), JGR: Planets, 125(6), e2020JE006387. [8] Lognonné, P., et al. (2020). Nat. Geo., 13, 213-220. [9] Golombek, M. et al., Submitted to SSR. [10] Murdoch, N., et al. (2017). SSR, 211, 429-455. [11] Farley, K. A., et al. (2020). SSR, 216, 1-41. [12] Mimoun, D., et al. (2023). SSR, 219(1), 5. [13] Maurice, S., et al. (2021). SSR, 217, 1-108. [14] Maurice, S. et al. (2022) Nature 605, 653-658. [15] Murdoch, N. et al., (2022) Nat. Comm., 13(1), 7505.