Winds at the Phoenix landing site

Abstract

[1] Wind speeds and directions were measured on the Phoenix Lander by a mechanical anemometer, the so-called Telltale wind indicator. Analysis of images of the instrument taken with the onboard imager allowed for evaluation of wind speeds and directions. Daily characteristics of the wind data are highly turbulent behavior during midday due to daytime turbulence with more stable conditions during nighttime. From L s ∼77°-123°winds were generally ∼4 m s −1 from the east, with 360°rotation during midday. From L s ∼123°-148°d aytime wind speeds increased to an average of 6-10 m s −1 and were generally from the west. The highest wind speed recorded was 16 m s −1 seen on L s ∼147°. Estimates of the surface roughness height are calculated from the smearing of the Kapton part of the Telltale during image exposure due to a 3 Hz turbulence and nighttime wind variability. These estimates yield 6 ± 3 mm and 5 ± 3 mm, respectively. The Telltale wind data are used to suggest that Heimdal crater is a source of nighttime temperature fluctuations. Deviations between temperatures measured at various heights are explained as being due to winds passing over the Phoenix Lander. Events concerning sample delivery and frost formation are described and discussed. Two different mechanisms of dust lifting affecting the Phoenix site are proposed based on observations made with Mars Color Imager on Mars Reconnaissance Orbiter and the Telltale. The first is related to evaporation of the seasonal CO 2 ice and is observed up to L s ∼95°. These events are not associated with increased wind speeds. The second mechanism is observed after L s ∼111°and is related to the passing of weather systems characterized by condensate clouds in orbital images and higher wind speeds as measured with the Telltale.

Effects of rolling on wind-induced detachment thresholds of volcanic glass on Mars

“…Aeolian processes on planet Mars commonly require wind speeds of several tens of meters per second to reach the fluid or static threshold when individual particles are entrained by the force of the wind (Greeley et al, 1974(Greeley et al, , 1980Greeley and Iversen, 1985;Iversen and White, 1982). However, wind speed measurements in the atmospheric boundary layer by Mars lander instrumentation (Hess et al, 1977;Holstein-Rathlou et al, 2010;Magalhães et al, 1999;Schofield et al, 1997, Sutton et al, 1978 and predictions from global atmospheric circulation models (e.g., Haberle et al, 2003;Michaels and Rafkin, 2004) indicate that common diurnal winds infrequently reach the required magnitude for sand transport. Observations of aeolian features such as dunes show a clearly different story, and illustrate that sands are much more actively transported by winds in the present-day Martian surface environment than what was previously thought possible (Bridges et al, 2012a, Hansen et al, 2011Bell, 2012b, Gardina et al, 2012;Silvestro et al, 2010).…”

Evaluating the Wind-Induced Mechanical Noise on the InSight Seismometers

“…However, a simple description of the wind sensor's resolution and accuracy is not readily available (Holstein-Rathlou et al 2010;Gunnlaugsson et al 2008;Chamberlain et al 1976).…”

“…Wind speeds and directions at a nominal height of 2 m above the Martian surface were measured by a mechanical anemometer, the so-called Telltale wind indicator (part of the Meteorological instrument packages; Gunnlaugsson et al 2008;Holstein-Rathlou et al 2010). We use all of the Phoenix Telltale experiment data that are available on the Planetary Data System.…”

Martian airfall dust on smooth, inclined surfaces as observed on the Phoenix Mars Lander telltale mirror

“…There are clear seasonal trends in the wind speed (HolsteinRathlou et al, 2010) and a clear diurnal trend in the wind direction (Holstein-Rathlou et al, 2010;Tamppari et al, 2010;Moores et al, 2010) a critical factor for accumulation on an inclined surface, such as the telltale mirror. Since dust can only arrive at the telltale mirror either through settling or via the action of wind, the lack of a correlation of the dustiness with diurnal or seasonal trends in wind is surprising.…”

“…This decrease started at 12:00 Local True Solar Time (LTST) with a worst-case time near 15:36 LTST and clearing into the evening hours. In addition to dust, frost condensed on the mirror at night (Holstein-Rathlou et al, 2010, 2011.…”