Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware

Abstract

Martian boundary layer wind speed and direction measurements, from a variety of locations, seasons and times, are provided. For each lander sent to Mars over the last four decades a unique record of the winds blowing during their descent is preserved at each landing site. By comparing images acquired from orbiting spacecraft of the impact points of jettisoned hardware, such as heat shields and parachutes, to a trajectory model the winds can be measured. We start our investigations with the Viking lander 1 mission and end with Schiaparelli. In-between we extract wind measurements based on observations of the Beagle 2, Spirit, Opportunity, Phoenix and Curiosity landing sites. With one exception the wind at each site during the lander's descent were found to be <8 m s −1. High speed winds were required to explain the displacement of jettisoned hardware at the Phoenix landing site. We found a tail wind (>20 m s −1), blowing from the northwest was required at a high altitude (>2 km) together with a gust close to the surface (<500 m altitude) originating from the north. All in all our investigations yielded a total of ten unique wind measurements in the PBL. One each from the Viking landers and one each from Beagle 2, Spirit, Opportunity and Schiaparelli. Two wind measurements, one above about 1 km altitude and one below, were possible from observations of the Curiosity and Phoenix landing site. Our findings are consistent with a turbulent PBL in the afternoon and calm PBL in the morning. When comparing our results to a GCM we found a good match in wind direction but not for wind speed. The information provided here makes available wind measurements previously unavailable to Mars atmosphere modellers and investigators.

A user-orientated column modelling framework for efficient analyses of the Martian atmosphere

“…circulation of the climate. Below 10 km, in situ wind meaurements (Paton et al, 2018), also indicate good agreement with GCM results in terms of wind direction perhaps reflecting the influence of the large scale circulation. However wind speed is less consistent with GCM results, perhaps reflecting some local influences from variations in topography or surface thermal properties at these altitudes.…”

Atmospheric Science with InSight

“…During the EDL, the measured deceleration through the atmosphere leads to the determination of atmospheric profiles along the trajectory as function of altitude with subkm vertical resolutions (down to hundreds of meters or better Magalhaes et al 1999) from the surface up to 130 km. The high-resolution sampling of atmospheric structure from surface to thermosphere during EDL complements remote sensing from orbiters, which provide global coverage at lower spatial resolution, orbiter aerobraking measurements, which carry out in situ measurements of density and temperature in the upper atmosphere, and lander (Paton et al 2018) measurements, which provide extended time series of high-accuracy measurements at one location. Past examples of such measurements are provided in Fig.…”

Response to reviewers #1 and #2

“…The similarity in temperature profiles above about 10 km is consistent with global circulation model (GCM) results and observations that suggest the temperature in this region of the atmosphere is largely controlled by the large-scale circulation of the climate. Below 10 km, in situ wind measurements (Paton et al, 2018) also indicate good agreement with GCM results in terms of wind direction, perhaps reflecting the influence of the large-scale circulation. However, wind speed is less consistent with GCM results, perhaps reflecting some local influences from variations in topography or surface thermal properties at these altitudes.…”