manuscript submitted to ESS 1 Listening for the Mars 2020 Landing Sequence with InSight 2 Listening for the Landing: Seismic Detections of 3 Perseverance's arrival at Mars with InSight 1 2 3;4 4 Benjamin Fernando , Natalia W´ojcicka , Marouchka Froment , Ross 5;6 7 8 2 5 Maguire , Simon C. St¨ahler , Lucie Rolland , Gareth S. Collins , Ozgur 9 3 10 11 6 Karatekin , Carene Larmat , Eleanor K. Sansom , Nicholas A. Teanby , 12;13 5 14 7 Aymeric Spiga , Foivos Karakostas , Kuangdai Leng , Tarje 1 4 7 4 8 Nissen-Meyer , Taichi Kawamura , Domenico Giardini , Philippe Lognonn´e , 15 16 9 Bruce Banerdt , Ingrid J. Daubar 1 10 Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 4AR, UK 2 11 Department of Earth Science and Engineering, Imperial College, London, SW7 2AZ, UK 3 12 Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA 4 13 Universit´ede Paris, Institut de Physique du Globe de Paris, CNRS, Paris, France 5 14 Department of Geology, University of Maryland, College Park, MD, USA 6 15 Department of Computational Mathematics, Science, and Engineering, Michigan State University, East 16 Lansing, MI, USA 7 17 Department of Earth Sciences, ETH Zurich, Sonneggstrasse 5, 8092 Z¨urich, Switzerland 8 18 Universit´eC^oted'Azur, Observatoire de la C^oted'Azur, CNRS, IRD, G´eoazur,France 9 19 Royal Observatory of Belgium, Belgium 10 20 Space Science and Technology Centre, Curtin University, Australia 11 21 School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 22 1RJ, UK 12 23 Laboratoire de M´et´eorologieDynamique / Institut Pierre-Simon Laplace (LMD/IPSL), Sorbonne 24 Universit´e,Centre National de la Recherche Scientifique (CNRS), Ecole´ Polytechnique, Ecole´ Normale 25 Sup´erieure(ENS), Campus Pierre et Marie Curie BC99, 4 place Jussieu 75005 Paris, France 13 26 Institut Universitaire de France (IUF), 1 rue Descartes, 75005 Paris, France 14 27 Scientific Computing Department, Rutherford Appleton Laboratory, Harwell, UK 15 28 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA 16 29 Earth, Environment and Planetary Sciences, Brown University, Providence, RI, USA 30 Key Points: 31 • The entry, descent and landing of Mars 2020 (NASA's Perseverance Rover) will 32 act as a seismic source on Mars 33 • We evaluate the detectability of the acoustic (atmospheric) and elastodynamic seis- 34 mic (ground) signals 35 • We predict the acoustic signal will not likely be detectable by InSight, but the seis- 36 mic signal may be. Corresponding author: Benjamin Fernando, [email protected] {1{ manuscript submitted to ESS 37 Abstract 38 The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance rover 39 will act as a seismic source of known temporal and spatial localization. We evaluate whether 40 the signals produced by this event will be detectable by the InSight lander (3452 km away), 41 comparing expected signal amplitudes to noise levels at the instrument. Modeling is un- 42 dertaken to predict the propagation of the acoustic signal (purely in the atmosphere), 43 the seismoacoustic signal (atmosphere-to-ground coupled), and the elastodynamic seis- 44 mic signal (in the ground only). Our results suggest that the acoustic and seismoacous- 45 tic signals, produced by the atmospheric shockwave from the EDL, are unlikely to be 46 detectable due to the pattern of winds in the martian atmosphere and the weak air-to- 47 ground coupling, respectively. However, the elastodynamic seismic signal produced by 48 the impact of the spacecraft's cruise balance masses on the surface may be detected by 49 InSight. The upper and lower bounds on predicted ground velocity at InSight are 2:0× −14 −1 −10 −1 50 10 ms and 1:3×10 ms . The upper value is above the noise floor at the time 51 of landing 40% of the time on average. The large range of possible values reflects uncer- 52 tainties in the current understanding of impact-generated seismic waves and their sub- 53 sequent propagation and attenuation through Mars. Uncertainty in the detectability also 54 stems from the indeterminate instrument noise level at the time of this future event. A 55 positive detection would be of enormous value in constraining the properties of the mar- 56 tian atmosphere, crust, and mantle as well as in improving our understanding of impact- 57 generated seismic waves. 58 Plain Language Summary 59 When it lands on Mars, NASA's Perseverance Rover will have to slow down rapidly 60 to achieve a safe landing. In doing this, it will produce a sonic boom and eject two large 61 balance masses which will hit the surface at very high speed. The sonic boom and bal- 62 ance mass impacts will produce seismic waves which will travel away from Perseverance's 63 landing site. Here we evaluate whether these seismic waves will be detectable by instru- 64 ments on the InSight lander (3452 km away). We predict that the waves from the bal- 65 ance mass impacts may be detectable. If the waves are recorded by InSight, this would 66 represent the first detection of ground motion generated by a seismic source on Mars at 67 a known time and location. This would be of enormous value in advancing our under- 68 standing of the structure and properties of Mars' atmosphere and interior as well as in 69 improving our understanding of impact-generated seismic waves. 70 1 Introduction 71 1.1 Motivation 72 NASA's Interior Exploration using Seismic Investigations, Geodesy and Heat Trans- 73 port (InSight) mission landed on Mars' Elysium Planitia in November 2018, and since 74 then has detected a number of `marsquake' events which are thought to be geologicaltec- 75 tonic in origin (Banerdt et al., 2020). 76 InSight faces a number of peculiar challenges associated with single-station seis- 77 mology (Panning et al., 2015). Without independent constraints on source properties, 78 robust seismic inversions are more challenging than they would be on Earth. Impact events 79 (where meteoroids hit the planet's surface) offer an opportunity to overcome some of these 80 challenges as they can be photographically constrained in location, size and timing from 81 orbital images. In theory, this should allow a positive impact detection to be used as 82 `calibration' for other seismic measurements. 83 However, no impact events have yet been conclusively detected and identified by 84 InSight, despite pre-landing expectations that impacts would make a significant contri- {2{ manuscript submitted to ESS 85 bution to martian seismicity (Daubar et al., 2018). A meteorite impact which formed 86 a new 1.5 m impact crater only 37 km from InSight in 2019 was not detected (Daubar 87 et al., 2020). 88 A number of possible reasons may explain the absence of impact detections thus 89 far. These include uncertainties in the impactor flux entering Mars' atmosphere (Daubar 90 et al., 2013) and in the seismic efficiency (the fraction of impactor kinetic energy con- 91 verted into seismic energy) of ground impacts that form metre-scale craters (W´ojcicka 92 et al., 2020), as well as high ambient noise through much of the day, which makes de- 93 tecting faint signals challenging. Should a seismic signal excited by an impact be detected, 94 distinguishing it from tectonic events remains challenging due to intense scattering in 95 the shallow crust of Mars (see van Driel et al. (2019) or Daubar et al. (2020) for further 96 discussion). 97 If a seismic signal recorded by InSight could be identified as impact-generated, con- 98 clusive attribution to a particular spatial and temporal location would require identifi- 99 cation of a new crater on the surface. Sparse orbital imaging coverage of the martian sur- 100 face at the required resolution, coupled with large error bounds on event distance and 101 azimuth estimations (e.g. Giardini et al. (2020)), make this extremely challenging. This 102 The use of orbital imagery also excludes seismic offers no information about seismic or in- 103 frasonic signals induced by those impactors which either burn up or explode in the at- 104 mosphere as airburst events (Stevanovi´cet al., 2017) and do not form new craters. 105 These challenges may be overcome by using as seismic sources the Entry, Descent, 106 and Landing (EDL) sequences of objects with known entry ephemerides (meaning a 107 priori calculated or independently constrained entry/re-entry timings and locations. 108 On Mars, a very limited number of events with known atmospheric entry ephemerides, and therefore a 109 priori known times and locations. The Mars 2020 mission, landing in February 2021, offers 110 an opportunity for this possible measurement. 111 1.2 Terrestrial and lunar context 112 Spacecraft re-entering the atmosphere are comparatively common on Earth. 113 These have trajectories which are often known prior to their arrival, meaning that 114 seismic observation campaigns can be planned in advance. This has been done for a 115 variety of spacecraft, including the Apollo command capsules (Hilton & Henderson, 116 1974), the Space Shuttle (Qamar, 1995; de Groot-Hedlin et al., 2008), Hayabusa-1 117 (Ishihara et al., 2012), Genesis (ReVelle et al., 2005) and Stardust (ReVelle & Ed- 118 wards, 2007). In these cases, seismic and infrasonic data were used to study the entry 119 dynamics of the spacecraft in question, for example the mechanics of energy dissipation 120 into the atmosphere. 121 Naturally occurring impact events on Earth may not have trajectories which 122 are known in advance, but their flight paths may be independently reconstructed from 123 photographic evidence (e.g. Devillepoix et al.