Global dust storms on Mars occur in some years but not in others. If the four Mars years of Viking data are representative, some distinguishing characteristics can be inferred. In years with global dust storms, dust is raised in the southern hemisphere and spread over much of the planet by an intensified Hadley circulation. In years without global dust storms, dust is raised in the northern hemisphere by relatively active mid-latitude storm systems but does not spread globally. In both cases the dusty season is winter in the north. Assuming that the cross-equatorial Hadley circulation plays a key role in the onset of global dust storms, it is shown from numerical simulations that a northern hemisphere dust haze weakens its intensity and, hence, its contribution to the surface stress in the southern hemisphere. This, in turn, reduces the possibility of global dust storm development. The interannual variability is therefore the result either of a competition between circulations in opposite hemispheres, in which case the variability has a random component, or it is the result of the cycling of dust between hemispheres, in which case the variability is related to the characteristics of global dust storms themselves.

The Rover Environmental Monitoring Station (REMS) instrument is on board NASA's Mars Science Laboratory (MSL) Curiosity rover. REMS has been measuring surface pressure, air, and ground brightness temperature, relative humidity, and ultraviolet (UV) irradiance since MSL's landing in 2012. In Mars Year (MY) 34 (2018) a global dust storm reached Gale Crater at Ls ~ 190°. REMS offers a unique opportunity to better understand the impact of a global dust storm on local environmental conditions, which complements previous observations by the Viking landers and Mars Exploration Rovers. All atmospheric variables measured by REMS are strongly affected albeit at different times. During the onset phase, the daily maximum UV radiation decreased by 90% between sols 2075 (opacity ~1) and 2085 (opacity ~8.5). The diurnal range in ground and air temperatures decreased by 35 and 56 K, respectively, with also a diurnal‐average decrease of ~2 and 4 K respectively. The maximum relative humidity, which occurs right before sunrise, decreased to below 5%, compared with prestorm values of up to 29%, due to the warmer air temperatures at night, while the inferred water vapor abundance suggests an increase during the storm. Between sols 2085 and 2130, the typical nighttime stable inversion layer was absent near the surface as ground temperatures remained warmer than near‐surface air temperatures. Finally, the frequency domain behavior of the diurnal pressure cycle shows a strong increase in the strength of the semidiurnal and terdiurnal modes peaking after the local opacity maximum, also suggesting differences in the dust abundance inside and outside Gale.

Abstract Martian planet-encircling dust storms or global dust storms (GDS), resulting from the combined influence of local and regional storms, are uncommon aperiodic phenomena: with an average frequency of approximately one every 3–4 MY, they produce a substantial rise in the atmospheric dust loading that lasts from weeks to months and have a significant impact on the atmospheric properties, energy budget, and global circulation. During the 2018/MY34 global dust storm, initiated at LS = 185° (30–31 May 2018), an intensive atmospheric science campaign was carried out by the Mars Science Laboratory (MSL) rover to monitor the environmental parameters at Gale Crater. We contribute to previous studies with independent retrievals to constrain the dust opacity and characterise the aerosol particle properties, including: size, shape and single scattering phase function. An iterative radiative transfer retrieval procedure was implemented to determine the aerosol parameters that best fit the angular distribution of sky radiance at forward and backward scattering regions observed by MSL Navigation Cameras (Navcams) during the 2018/MY34 GDS. The MOPSMAP aerosol database and Double Henyey-Greenstein (DHG) analytical single scattering phase functions were used to model the Martian dust aerosol. Outcomes of this study show a steep rise in dust opacity from pre-storm levels of 1.2 up to τ > 9, correlated to particle size variations from 1 to 4 μm. DHG phase functions are characterised with an average asymmetry parameter of g = 0.60 ± 0.11 during the storm, diverging from values of around 0.71 ± 0.06 for the same period in previous MY. Best fitting simulations to backscatter observations for high-opacity periods were generated by a mixture of spheroids following a log-normal distribution of aspect ratios centred on 2.8 ± 0.9, in contrast to values of 1.8 in post-storm sols, thus pointing to more irregular particle shapes at the peak of the dust storm.

Dust storm activity in the Aonia-Solis-Valles Marineris (ASV) region is analyzed using data collected from 8 Mars years of Mars Daily Global Maps. During L s = 120°-180°, dust storms within the ASV region tend to organize into dust storm sequences, making ASV an important storm track in the southern hemisphere outside the conventional dust storm season. In late southern winter, the ASV region is influenced by a combination of strong time-mean winds, synoptic eddies, and tidal winds. The ASV dust storm sequences can increase the background dust opacity and sometimes significantly influence the large-scale atmospheric thermal structure and planetary waves. They can be divided into two groups - one with large size and long duration; the other with small size and mostly short duration. The time series of storm area exhibits a pseudo-periodicity near 20 sols. This periodicity is similar to that found in eddy kinetic energy and traveling waves and to the Baroclinic Annular Mode of the terrestrial atmosphere.

Nucleation onto atmospheric ions has been predicted to affect the evolution and lifetime of haze layers on Titan, Neptune, and Triton. Atmospheric electrical processes on Titan, pre-Huygens, are summarised. Closer to Earth, heating from solar radiation dominates planetary meteorology; however Mars may have a global circuit based on electrical discharges from dust storms. There is a need for direct measurements of planetary atmospheric electrification, in particular on Mars, to assess the risk for future missions. Theoretical understanding could be increased by cross-disciplinary work to modify and update models and parameterisations initially developed for specific planetary atmospheres to make them more broadly applicable. Published as: Surveys in Geophysics, 27, 1, pp 63-108 (2006) DOI: 10.1007/s10712-005-0642-9 arXiv categories: physics.geo-ph physics.ao-ph physics.space-ph

Introduction: We have captured Martian dust and weather over 25 years of continuous satellite observations. Using thermal infrared (IR) data from instruments like TES (Mars Global Surveyor), THEMIS (Mars Odyssey), MCS (Mars Reconnaissance Orbiter), and EMIRS (Emirates Mars Mission), we have produced diurnal maps of column dust optical depth (CDOD) covering 13 Martian years (MY 24–37) [1–5]. Two types of maps are available: gridded maps (incomplete) and kriged maps (complete). These maps, normalized to 610 Pa or expressed as total CDOD, are mainly used as “dust scenarios” in the Mars Climate Database [6] and are publicly available (see the links to the datasets in the acknowledgments section). While they have helped study dust seasonality and large-scale storms, their use in multi-annual and daily-scale analyses remains limited.Latest advances: Starting from retrievals provided by the TES, MCS, and EMIRS science teams, we use two processing chains (gridding and kriging) to produce daily quasi-complete gridded CDOD maps and fully complete kriged CDOD maps. These chains were technically improved and scientifically enhanced with the following changes:1. We have used a new tool for Earth – Mars datetime conversion [13] to define a sol of the year for each daily map using a sol-based Mars calendar, as described in [1, Appendix A].2. We have changed the computation of the total CDOD (defined in [1]) by using a lookup table of surface pressure extracted from the MCD v5.3, interpolate

Introduction: We have currently accumulated over 25 years of continuous satellite data on Martian dust and, generally, on the weather of the Red Planet. By utilizing data from instruments operating in the thermal infrared such as the Thermal Emission Spectrometer (TES, onboard the Mars Global Surveyor satellite), Thermal Emission Imaging System (THEMIS, onboard Mars Odyssey), and Mars Climate Sounder (MCS, onboard the Mars Reconnaissance Orbiter), we have been able to reconstruct diurnal maps of column dust optical depth (CDOD) spanning more than 13 Martian years (MY) from 1999 to the present day [1, 2, 3, 4, 5]. Two types of maps exist: ‘gridded maps’ (the mesh is regular but values are missing where there are no observations) and ‘kriged maps’ (interpolated from the gridded maps using kriging to produce complete maps). These longitude-latitude maps are used as 'dust scenario' in the Mars Climate Database [6], among many other applications. They are routinely updated and made publicly available in NetCDF or FITS formats (see the links to the datasets in the acknowledgments section).Recent developments: The daily CDOD maps covering MY 24 through part of MY 27 have been recently improved by using revised retrievals of column dust optical depths from TES observations (refer to the link in the acknowledgments section for accessing this updated dataset). The top four panels of Figure 1 (MY 24, 25, 26, 27) show zonal means of these improved CDOD maps normal

The proportions of different gases are similar to those in the atmosphere of Venus (see Table 10.2), but a lot less of each gas is found in the thin air on Mars. While winds on Mars can reach high speeds, they exert much less force than wind of the same velocity would on Earth because the atmosphere is so thin. The wind is able, however, to loft very fine dust particles, which can sometimes develop planet-wide dust storms. It is this fine dust that coats almost all the surface, giving Mars its distinctive red color. In the absence of surface water, wind erosion plays a major role in sculpting the martian surface (Figure 10.24). The issue of how strong the winds on Mars can be plays a big role in the 2015 hit movie The Martian in which the main character is stranded on Mars after being buried in the sand in a windstorm so great that his fellow astronauts have to leave the planet so their ship is not damaged. Astronomers have noted that the martian winds could not possibly be as forceful as depicted in the film because the air pressure is so low. In most ways, however, the depiction of Mars in this movie is remarkably accurate.

Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance. Mars is a desert-like rocky planet with a tenuous atmosphere that is primarily carbon dioxide (CO2). At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from −153 to 20 °C (−243 to 68 °F), and cosmic radiation is high. Mars r Despite repeated detections of methane on Mars, there is no scientific consensus as to its origin. One suggestion is that methane exists on Mars and that its concentration fluctuates seasonally. The existence of methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars, or by Martian life. Compared to Earth, its higher concentration of atmospheric CO2 and lower surface pressure may be why sound is attenuated more on Mars, where natural sources are rare apart from the wind. Using acoustic recordings collected by the Perseverance rover, researchers concluded that the speed of sound there is approximately 240 m/s for frequencies below 240 Hz, and 250… Mars has seasons, alternating between its northern and southern hemispheres, similar to on Earth. Additionally the orbit of Mars has, compared to Earth's, a large eccentricity and approaches perihelion when it is summer in its southern hemisphere and winter in its northern, and aphelion when it is winter in its southern hemisphere and summer in its northern. As a result, the seasons in its southern hemisphere are more extreme and the seasons in its northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to 30 °C (54 °F). Martian surface temperatures vary from lows of about −110 °C (−166 °F) to highs of up to 35 °C (95 °F) in equatorial summer. The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure (about 1% that of the atmosphere of Earth), and the low thermal inertia of Martian soil. The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. Mars has the largest dust storms in the Solar System, reaching speeds of over 160 km/h (100 mph). These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase global temperature. Seasons also produce dry ice covering polar ice caps. T…

Mahaffy, Paul R. (13 November 2020). "Hydrogen escape from Mars is driven by seasonal and dust storm transport of water". Science. 370 (6518): 824–831. Bibcode:2020Sci A number of significant scientific events occurred in 2020. 11 November Astronomers report newly found evidence for volcanic activity as recently as 53–210 kya on the planet Mars. Such activity could have provided the environment, in terms of energy and chemicals, needed to support life forms. Scientists report the detection of SARS-CoV-2 receptor-binding domain antibodies in 111 (11.6%) of 959 asymptomatic individuals of a lung cancer screening trial in Italy, starting from 3 September 2019, apparently establishing a substantially earlier start time of the COVID-19 pandemic. However, the journal published an expression of concern in March 2021 due to possible issues with the peer review. 12 November – Scientists report the development of a microalgae-based fish-free aquaculture feed with substantial gains in sustainability, performance, economic viability, and human health. 13 November – Scientists report that Mars' current loss of atomic hydrogen from water is largely driven by seasonal processes and dust storms that transport water directly to the upper atmosphere and that this has influenced the planet's climate. 16 November Results of phase III trials of Moderna's mRNA vaccine are announced, the company claims to 94.5% reduction of COVID-19 cases based on interim results, including severe illnesses. The vaccine is easier to distribute than BNT162b2 as no ultra-cold storage is required. ALMA staff release a corrected version of the data used by other scientists in a study published on 14 September that claimed an apparent detection of phosphine in Venus' atmosphere. On the same day authors of this study publish a re-analysis as a preprint using the new data that concludes the planet-averaged PH3 abundance to be ≈7 times lower than what they detected with data of the previous ALMA processing, to vary by location and to be reconcilable with the JCMT detection of ≈20 times this abundance if substantially varying in time. They also respond to points raised in a preprint that challenged their conclusions in October and find that so far no other compound can explain the data. ALMA is reported to be expected to restart in early 2021 after a shutdown due to the COVID-19 crisis and may enable further observations that could…