The NASA Mars Science Laboratory (MSL) rover, Curiosity, has safely landed near a 35-km-long dark dune field in Gale Crater on Mars. This dune field crosses the landing site from the northeast to the southwest and lies along Curiosity’s traverse to Aeolis Mons. Here we present the first evidence of recent aeolian activity in the form of ripple and dune migration, and further estimate wind directions within the dune field through analysis of ripple and dune morphologies and the Mars Regional Atmospheric Modeling System (MRAMS). We measured a minimum ripple migration rate of 0.66 m per Earth year, and dune migration rate of 0.4 m per Earth year, in the southwest portion of the field. A strongly bidirectional ripple crestline orientation, nearly orthogonal dune slipfaces, and linear seif or oblique dunes indicate a bidirectional wind regime with winds mainly coming from the ENE and from the northwest; however, MRAMS results indicate primary winds from the ENE. Our constraints on the wind regime provide the unique opportunity to use ground measurements from MSL to test the accuracy of winds predicted from orbital data.

Mineral dust particles represent the most abundant component of atmospheric aerosol in terms of dry mass. They play a key role in climate and climate change, so the study of their emission processes is of utmost importance. Measurements of dust emission into the atmosphere are scarce, so that the dust load is generally estimated using models. It is known that the emission process can generate strong atmospheric electric fields. Starting from the data we acquired in the Sahara desert, here, we show for the first time that depending on the relative humidity conditions, electric fields contribute to increase up to a factor of 10 the amount of particles emitted into the atmosphere. This means that electrical forces and humidity are critical quantities in the dust emission process and should be taken into account in climate and circulation models to obtain more realistic estimations of the dust load in the atmosphere.

The first in situ investigation of an active dune field on another planetary surface occurred in 2015–2016 when the Mars Science Laboratory Curiosity rover investigated the Bagnold Dunes on Mars. High Resolution Imaging Science Experiment images show clear seasonal variations that are in good agreement with atmospheric model predictions of intra‐annual sand flux and migration directions that together indicate that the campaign occurred during a period of low wind activity. Curiosity surface images show that limited changes nevertheless occurred, with movement of large grains, particularly on freshly exposed surfaces, two occurrences of secondary grain flow on the slip face of Namib Dune, and a slump on a freshly exposed surface of a large ripple. These changes are seen at Martian solar day (sol)‐to‐sol time scales. Grains on a rippled sand deposit and unconsolidated dump piles show limited movement of large grains over a few hours during which mean friction speeds are estimated at 0.3–0.4 m s⁻¹. Overall, the correlation between changes and peak Rover Environmental Monitoring Station (REMS) winds is moderate, with high wind events associated with changes in some cases, but not in others, suggesting that other factors are also at work. The distribution of REMS 1 Hz wind speeds shows a significant tail up to the current 20 m s⁻¹ calibration limit, indicating that even higher speed winds occur. Nonaeolian triggering mechanisms are also possible. The low activity period at the dunes documented by Curiosity provides clues to processes that dominated in the Martian past under conditions of lower obliquity.

Aeolian megaripples, with 5‐ to 50‐m spacing, are abundant on the surface of Mars. These features were repeatedly targeted by high‐resolution orbital images, but they have never been observed to move. Thus, aeolian megaripples (especially the bright‐toned ones often referred as Transverse Aeolian Ridges—TARs) have been interpreted as relict features of a past climate. In this report, we show evidence for the migration of bright‐toned megaripples spaced 1 to 35 m (5 m on average) in two equatorial areas on Mars indicating that megaripples and small TARs can be active today. The moving megaripples display sand fluxes that are 2 orders of magnitudes lower than the surrounding dunes on average and, unlike similar bedforms on Earth, can migrate obliquely and longitudinally. In addition, the active megaripples in the two study areas of Syrtis Major and Mawrth Vallis show very similar flux distributions, echoing the similarities between dune crest fluxes in the two study areas and suggesting the existence of a relationship between dune and megaripple fluxes that can be explored elsewhere. Active megaripples, together with high‐sand flux dunes, represent a key indicator of strong winds at the surface of Mars. A past climate with a denser atmosphere is not necessary to explain their accumulation and migration.