Mars

Mars

Sources #

Focus areas #

Maps #

There are many maps of Mars. Here are some notable ones:

Quadrangles #

Quadrangles on Mars have the MC prefix.

In 1979, NASA published ATLAS OF MARS: THE 1:5,000,000 MAP SERIES, edited by R.M. Batson, P.M. Bridges, and J.L. Inge, of the U.S. Geological Survey in Flagstaff, Arizona. This was a compendium of airbrushed shaded relief maps, controlled photomosaics, and in a few cases albedo (shading) maps, mostly assembled from Mariner 9 survey images, with some gaps filled by Viking orbiter images. The planet was divided into thirty “quadrangles” or areas, each with an “Mars Chart” or “MC” number (MC-1 through MC-30). The equatorial region was portrayed in the Mercator projection, with Lambert Conformal Conic for the mid-latitudes and Polar Stereographic for the poles.

Although digital products such as the Mars Digital Image Mosaic (MDIM) and various Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) maps have partially supplanted the ATLAS, it remains a standard desktop reference today.

In 1999, the Mars Orbiter Camera (MOC) aboard the MGS orbiter acquired a global stereo image dataset using its red-filter Wide Angle Camera. We have recently completed a 256 pixel/degree (about 230 meters/pixel) mosaic of these images using software developed at Malin Space Science Systems (MSSS). Visit the MSSS Geodesy Campaign Mosaic Page to access both partial and full-resolution mosaics in Planetary Data System format.

Geological maps #

https://pubs.usgs.gov/sim/3292/pdf/sim3292_map.pdf ( backup )

Surface #

Radiation level #

The martian surface is quite radioactive. Assuming 1Gy = 1Sv (may be roughly ok given that we’re talking about background radiation), a year on Mars exposes people easily to radiation levels that have a clear correlation with cancer risk.

https://mars.nasa.gov/resources/21336/solar-storms-radiation-at-martian-orbit-and-surface/

Energetic particles from a large solar storm in September 2017 were seen both in Mars orbit and on the surface of Mars by NASA missions to the Red Planet.

The horizontal axis for both parts of this graphic is the time from Sept. 10 to Sept. 15, 2017. The upper portion of this graphic shows the increase in protons in two ranges of energy levels (15- to-100 million electron volts and 80-to-220 million electron volts), as recorded by the Solar Energetic Particle instrument on NASA’s on NASA’s Mars Atmosphere and Volatile Evolution orbiter, or MAVEN. The lower portion shows the radiation dose on the Martian surface, in micrograys per day, as measured by the Radiation Assessment Monitor instrument on NASA’ Curiosity Mars rover. Micrograys are unit of measurement for absorbed radiation dose.

Note that only protons in the higher bracket of energy levels penetrate the atmosphere enough to be detected on the surface.

  • According to Wikipedia, the surface equivalent dose rate is of 27 uSv/h, so 27 uSv/h * 24h = 648 uSv/day = 0.65 mSv/day (https://www.science.org/doi/10.1126/science.1244797)

  • Annual dose on the martian surface: ~0.3mG * 365 ~= 100mG/y, and 0.65mSv * 365 ~= 237mSv/y about 5 times the max limit for exposure on the workplace and more than double than the minimum of annual radiation exposure clearly linked to cancer development.

https://photojournal.jpl.nasa.gov/catalog/PIA17601

Measurements with the MSL Radiation Assessment Detector (RAD) on NASA’s Curiosity Mars rover during the flight to Mars and now on the surface of Mars enable an estimate of the radiation astronauts would be exposed to on an expedition to Mars. NASA reference missions reckon with durations of 180 days for the trip to Mars, a 500-day stay on Mars, and another 180-day trip back to Earth. RAD measurements inside shielding provided by the spacecraft show that such a mission would result in a radiation exposure of about 1 sievert, with roughly equal contributions from the three stages of the expedition. A Sievert is a measurement unit of radiation exposure to biological tissue. This graphic shows the estimated amounts for humans on a Mars mission and amounts for some other activities.

For reference: https://xkcd.com/radiation/ 237mSv is already in the red zone.

xkcd-radiation.png

Soil toxicity #

From Wikipedia https://en.wikipedia.org/wiki/Martian_soil:

Martian soil is toxic, due to relatively high concentrations of perchlorate compounds containing chlorine. [...]

The report noted that one of the types of plant studied, Eichhornia crassipes, seemed resistant to the perchlorates and could be used to help remove the toxic salts from the environment, although the plants themselves would end up containing a high concentration of perchlorates as a result. There is evidence that some bacterial lifeforms are able to overcome perchlorates by physiological adaptations to increasing perchlorate concentrations, and some even live off them. However, the added effect of the high levels of UV reaching the surface of Mars breaks the molecular bonds, creating even more dangerous chemicals which in lab tests on Earth were shown to be more lethal to bacteria than the perchlorates alone.

From “Perchlorate-specific proteomic stress responses of Debaryomyces hansenii could enable microbial survival in Martian brines”, Jacob Heinz, Joerg Doellinger, Deborah Maus, Andy Schneider, Peter Lasch, Hans-Peter Grossart, Dirk Schulze-Makuch

Dust #

Martian dust itself is likely carcirogenic, because it’s fine and reactive, two key traits of dusts that cause asbestosis (see quotes below), and toxic, as it contains very high levels of perchlorates that are toxic to humans and to the majority of plants and bacteria (see section on soil)

From Wikipedia: https://en.wikipedia.org/wiki/Martian_soil

The potential danger to human health of the fine Martian dust has long been recognized by NASA. A 2002 study warned about the potential threat, and a study was carried out using the most common silicates found on Mars: olivine, pyroxene and feldspar. It found that the dust reacted with small amounts of water to produce highly reactive molecules that are also produced during the mining of quartz and known to produce lung disease in miners on Earth, including cancer.

Dust storms #

https://photojournal.jpl.nasa.gov/catalog/PIA25361:

This series of images from a navigation camera aboard NASA’s Perseverance rover shows a gust of wind sweeping dust across the Martian plain beyond the rover’s tracks on June 18, 2021 (the 117th sol, or Martian day, of the mission). The dust cloud in this GIF was estimated to be about 1.5 square miles (4 square kilometers) in size; it was the first such Martian wind-lifted dust cloud of this scale ever captured in images. This image has been enhanced in order to show maximal detail, with some color distortion. (my note: probably contrast, as the sky is too white to be correct).

From Wikipedia again:

However, under current Martian conditions, the mass movements involved are generally much smaller than on Earth. Even the 2001 global dust storms on Mars moved only the equivalent of a very thin dust layer – about 3 µm thick if deposited with uniform thickness between 58° north and south of the equator. Dust deposition at the two rover sites has proceeded at a rate of about the thickness of a grain every 100 sols.

Reference: https://arxiv.org/pdf/cond-mat/0603656.pdf ( backup )

Dust storms are violent but not as much as on Earth. They tend to occurr when it’s summer in the southern hemisphere, due to the closeness of the planet to the Sun (Mar’s orbit is way more eccentric than Earth’s) which triggers much stonger temperature swings on the surface and therefore larger atmospheric movements.

Mars’ dust storms don’t reach the strenght of a terrestrial hurricane. The air pressure at surface level is just a hundredth of Earth’s and the wind speeds are just half of what would be considered hurricane wind on Earth.

Dust devil, Curiosity: https://photojournal.jpl.nasa.gov/catalog/PIA24039

NASA’s Curiosity Mars rover spotted this dust devil with one of its Navigation Cameras around 11:35 a.m. local Mars time on Aug. 9, 2020 (the 2,847th Martian day, or sol, of the mission). The frames in this GIF were shot over 4 minutes and 15 seconds. Taken from the “Mary Anning” drill site, this dust devil appears to be passing through small hills just above Curiosity’s present location on Mount Sharp. The dust devil is approximately one-third to a half-mile (half-a-kilometer to a kilometer) away and estimated to be about 16 feet (5 meters) wide. The dust plume disappears past the top of the frame, so an exact height can’t be known, but it’s estimated to be at least 164 feet (50 meters) tall. Contrast has been modified to make frame-to-frame changes easier to see.

https://www.esa.int/About_Us/ESAC/Mars_dust_storm

The high resolution stereo camera on board ESA’s Mars Express captured this impressive upwelling front of dust clouds – visible in the right half of the frame – near the north polar ice cap of Mars in April this year (2018).

It was one of several local small-scale dust storms that have been observed in recent months at the Red Planet, which is currently enduring a particularly intense dust storm season. A much larger storm emerged further southwest at the end of May and developed into a global, planet-encircling dust storm within several weeks.

Dust storms on Mars occur regularly during the southern summer season when the planet is closer to the Sun along its elliptical orbit. The enhanced solar illumination causes stronger temperature contrasts, with the resulting air movements more readily lifting dust particles from the surface – some of which measure up to about 0.01 mm in size.

Martian dust storms are very impressive, both visually like in this image and in terms of the intensity and duration of the rarer global events, but they are generally weaker compared to hurricanes on Earth. Mars has a much lower atmospheric pressure – less than one hundredth of Earth’s atmospheric pressure at the surface – and martian storms have less than half the typical wind speeds of hurricanes on Earth.

This colour image was created using data from the nadir channel, the field of view of which is aligned perpendicular to the surface of Mars, and the colour channels of the high-resolution stereo camera. The ground resolution is approximately 16 m/pixel and the images are centred at about 78°N/106°E.

Atmosphere #

Fixed-wing flight #

https://www.x-plane.com/adventures/mars.html

https://marsairplane.larc.nasa.gov/

Sound #

Sound on Mars propagates little due to the low air density and the fact that the atmosphere is mostly made of CO2. Outdoors is difficult to hear even sounds made by objects relatively close by.

On top of this, longer (lower frequency, low pitch) soundwaves arrive “ahead” of shorter, higher piched sounds, giving all sounds a sort of “underwater” roundness. The audio of the fall of a meteorite ( https://www.nasa.gov/feature/jpl/nasa-s-insight-hears-its-first-meteoroid-impacts-on-mars, backup ) shows how the sound of the fall sounds far more like a rock falling in water than the sharp, “dry” explosion that would be heard on Earth.

Other audio snippets: https://mars.nasa.gov/mars2020/multimedia/audio/

One interesting example is the sound of Ingenuity flying on Mars: https://mars.nasa.gov/resources/25893 ( backup )

Sky color #

The variability of the sky’s color is huge and seems to span from yellow-brown (horizon, midday), grayish (high to the zenith), pink-red (earlier and later in the day), violet (in presence of water-ice clouds) to white/blueish (sunset/sunrise). It also heavily varies in luminosity depending on the dust load.

On top of it, it’s always hard to understand how image colors are calibrated, so some may be quite off.

Wikipedia https://en.wikipedia.org/wiki/Astronomy_on_Mars:

It is now known that during the Martian day, the sky can vary from a pinkish-red to a yellow-brown “butterscotch” color. Around sunset and sunrise, the sky is rose in color, but in the vicinity of the setting Sun it is blue. This is the opposite of the situation on Earth. Twilight lasts a long time after the Sun has set and before it rises because of the dust high in Mars’s atmosphere.

https://photojournal.jpl.nasa.gov/catalog/PIA01546 https://web.archive.org/web/20040810170442/ http://humbabe.arc.nasa.gov/mgcm/faq/sky.html

The true color of Mars based upon three filters with the sky set to aluminance of 60. The color of the Pathfinder landing site is yellowish brown with only subtle variations. These colors are identical to the measured colors of the Viking landing sites reported by Huck et al. [1977]. This image was taken near local noon on Sol 10. A description of the techniques used to generate this color image from IMP data can be found in Maki et al., 1999. Note: a calibrated output device is required accurately reproduce the correct colors.

https://mars.nasa.gov/mer/spotlight/spirit/a12_20040128.html https://mars.nasa.gov/mer/spotlight/spirit/images/Pan_Dust_Seams_2_040115174827.jpg

Difference in sky color in Spirit’s first panoramic images, where frames show different levels of darkness, depending on the weather when each frame was taken (light dust conditions on the left, heavy dust on the right).

Time-lapse composite of the Martian horizon as seen by the Opportunity rover over 30 Martian days; it shows how much sunlight the July 2007 dust storms blocked; Tau of 4.7 indicates 99% sunlight was blocked.

Note: 99% is not much in absolute terms. It does not seem dark or night-like. Human eyes can easily adapt to differences in brightness up to a few orders of magnitude: 99% looks probably like a storm, but brighter than indoors lightning conditions.

https://mars.nasa.gov/resources/21916/shades-of-martian-darkness/

This series of images shows simulated views of a darkening Martian sky blotting out the Sun from NASA’s Opportunity rover’s point of view, with the right side simulating Opportunity’s current view in the global dust storm (June 2018). The left starts with a blindingly bright mid-afternoon sky, with the sun appearing bigger because of brightness. The right shows the Sun so obscured by dust it looks like a pinprick. Each frame corresponds to a tau value, or measure of opacity: 1, 3, 5, 7, 9, 11.

Note: I only found images from rovers measuring tau values up to about 5. I’m not sure whether the atmosphere ever goes to tau levels higher than that, but I didn’t do much research yet (not even on the mentioned June 2018 global dust storm).

Sunset, Mars Pathfinder (June 1999)

https://photojournal.jpl.nasa.gov/catalog/PIA01547

The brownish gray sky as it would be seen by an observer on Mars in this four-frame, true color mosaic taken on sol 24 (at approximately 1610 LST). The twin peaks can be seen on the horizon. The sky near the sun is a pale blue color. Azimuth extent is 60° and elevation extent is approximately 12°degrees. A description of the techniques used to generate this color image from IMP data can be found in Maki et al., 1999 (see full reference in Image Note). Note: a calibrated output device is required accurately reproduce the correct colors.

Sunset, Spirit (May 2005)

https://www.nasa.gov/multimedia/imagegallery/image_feature_347.html

On May 19, 2005, NASA’s Mars Exploration Rover Spirit captured this stunning view as the Sun sank below the rim of Gusev crater on Mars. This Panoramic Camera mosaic was taken around 6:07 in the evening of the rover’s 489th Martian day, or sol.

Sunset and twilight images are occasionally acquired by the science team to determine how high into the atmosphere the Martian dust extends, and to look for dust or ice clouds. Other images have shown that the twilight glow remains visible, but increasingly fainter, for up to two hours before sunrise or after sunset. The long Martian twilight (compared to Earth’s) is caused by sunlight scattered around to the night side of the planet by abundant high altitude dust. Similar long twilights or extra-colorful sunrises and sunsets sometimes occur on Earth when tiny dust grains that are erupted from powerful volcanoes scatter light high in the atmosphere.

Sunset, Curiosity (April 2015)

https://photojournal.jpl.nasa.gov/catalog/PIA19400

https://photojournal.jpl.nasa.gov/catalog/PIA19401

NASA’s Curiosity Mars rover recorded this view of the sun setting at the close of the mission’s 956th Martian day, or sol (April 15, 2015), from the rover’s location in Gale Crater.

This was the first sunset observed in color by Curiosity. The image comes from the left-eye camera of the rover’s Mast Camera (Mastcam). The color has been calibrated and white-balanced to remove camera artifacts. Mastcam sees color very similarly to what human eyes see, although it is actually a little less sensitive to blue than people are.

Dust in the Martian atmosphere has fine particles that permit blue light to penetrate the atmosphere more efficiently than longer-wavelength colors. That causes the blue colors in the mixed light coming from the sun to stay closer to sun’s part of the sky, compared to the wider scattering of yellow and red colors. The effect is most pronounced near sunset, when light from the sun passes through a longer path in the atmosphere than it does at mid-day.

Here an example of grey zenith sky, from inSight (4.5024°N 135.6234°E, Elysium Planitia). Source: Color_Properties_at_the_Mars_InSight_Landing_Site.pdf which also contains the entire analysis of sky and soil chromaticity (color properties) at the landing site.

imae

https://photojournal.jpl.nasa.gov/catalog/PIA00915

These clouds from Sol 15 have a new look. As water ice clouds cover the sky, the sky takes on a more bluish cast. This is because small particles (perhaps a tenth the size of the martian dust, or one-thousandth the thickness of a human hair) are bright in blue light, but almost invisible in red light. Thus, scientists expect that the ice particles in the clouds are very small. The clouds were imaged by the Imager for Mars Pathfinder (IMP).

Mars Pathfinder is the second in NASA’s Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

Photojournal note: Sojourner spent 83 days of a planned seven-day mission exploring the Martian terrain, acquiring images, and taking chemical, atmospheric and other measurements. The final data transmission received from Pathfinder was at 10:23 UTC on September 27, 1997. Although mission managers tried to restore full communications during the following five months, the successful mission was terminated on March 10, 1998.

Atmospheric water #

Average atmospheric pressure on Mars seems to be about 0.6kPa, which is precisely where the triple point of water lays. There is therefore an extremely slim possibility of liquid water on the surface at 0°C, but most often water is frozen.

The average surface temperature of Mars is -64°C, but variations are strong. At the equator, temperatures can go well above 0°C, in which case, ice sublimates.

Martian surface temperatures vary from lows of about -110 °C to highs of up to 35 °C in equatorial summer.

Wikipedia, from https://web.archive.org/web/20131102112312/http://marsrover.nasa.gov/spotlight/20070612.html

Phase diagram of water, for reference:

Fog #

Fog forms regularly on Mars in some locations. However, what are these conditions, and how dense, opaque, stable it is?

Snow & frost #

Snow is possible, but it normally does not reach the surface due to rapid sublimation mid-flight.

https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080929.html:

NASA’s Phoenix Mars Lander has detected snow falling from Martian clouds. […] A laser instrument designed to gather knowledge of how the atmosphere and surface interact on Mars has detected snow from clouds about 4 kilometers (2.5 miles) above the spacecraft’s landing site. Data show the snow vaporizing before reaching the ground.

In temperate and polar regions, Viking missions found snow and frost made of water and carbon dioxide.

https://photojournal.jpl.nasa.gov/catalog/PIA00571

This high-resolution color photo of the surface of Mars was taken by Viking Lander 2 at its Utopia Planitia landing site on May 18, 1979, and relayed to Earth by Orbiter 1 on June 7. It shows a thin coating of water ice on the rocks and soil. The time the frost appeared corresponds almost exactly with the buildup of frost one Martian year (23 Earth months) ago. Then it remained on the surface for about 100 days. Scientists believe dust particles in the atmosphere pick up bits of solid water. That combination is not heavy enough to settle to the ground. But carbon dioxide, which makes up 95 percent of the Martian atmosphere, freezes and adheres to the particles and they become heavy enough to sink. Warmed by the Sun, the surface evaporates the carbon dioxide and returns it to the atmosphere, leaving behind the water and dust. The ice seen in this picture, like that which formed one Martian year ago, is extremely thin, perhaps no more than one-thousandth of an inch thick.

Clouds #

There are several pictures of clouds on Mars. The catch is their thickness, because Martian clouds tend to be extremely fine and really hard to see.

These clouds were captured as part of a follow-on imaging campaign to study noctilucent, or “night-shining” clouds, which started in 2021. While most Martian clouds hover no more than 37 miles (60 kilometers) above the ground and are composed of water ice, these clouds appear to be higher in elevation, where it’s very cold. That suggests these clouds are made of carbon dioxide, or dry ice.

For reference, most commonly seen terrestrial clouds like cumulus form at only 2km from the surface and even cirrus, which are the highest we normally see, form around 3km up at the poles and up to 18km high at the equator, so not even a third of the average Martian cloud.

The closest we have on Earth to these high altitude clouds are Polar Stratospheric Clouds (PSCs) which form in the polar stratosphere at about 15-25km, and noctilucent clouds, which form in the mesosphere at around 80-85km. There are still well visible from the surface and look like cirri.

https://www.space.com/2812-mars-clouds-higher-earth.html

If you wanted to see these clouds from the surface of Mars, you would probably have to wait until after sunset" says Franck Montmessin, a French researcher who works with the camera team. This is because the clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds on Earth, which occur about 50 miles (80 kilometers) above our planet.

https://photojournal.jpl.nasa.gov/catalog/PIA24622

NASA’s Curiosity Mars rover captured these clouds just after sunset on March 19, 2021, the 3,063rd Martian day, or sol, of the rover’s mission. The image is made up of 21 individual images stitched together and color corrected so that the scene appears as it would to the human eye. The clouds are drifting over “Mont Mercou,” a cliff face that Curiosity has been studying.

Sky is visibly too white, so I doubt this is how they would be seen at the naked eye. They are probably contrast enhanced, but the caption does not mention.

Iridescent clouds

https://photojournal.jpl.nasa.gov/catalog/PIA24662

NASA’s Curiosity Mars rover spotted these iridescent, or “mother of pearl”, clouds on March 5, 2021, the 3,048th Martian day, or sol, of the mission. Seen here are five images stitched together from a much wider panorama taken by the rover’s Mast Camera, or Mastcam. The full panorama (Figure 1) was stitched together from 23 images.

Again, sky is visibly too white.

Drifting Clouds Over Mars’ Mount Sharp, Curiosity.

https://photojournal.jpl.nasa.gov/catalog/PIA24661

This GIF shows clouds drifting over Mount Sharp on Mars, as viewed by NASA’s Curiosity rover on March 19, 2021, the 3,063rd Martian day, or sol, of the mission. Each frame of the scene was stitched together from six individual images.

Same problem as the others.

https://photojournal.jpl.nasa.gov/catalog/PIA24645

https://photojournal.jpl.nasa.gov/catalog/PIA24646

Cirri at sunset, Curiosity.

Using the navigation cameras on its mast, NASA’s Curiosity Mars rover took these images of clouds just after sunset on March 31, 2021, the 3,075th so, or Martian day, of the mission. These noctilucent, or twilight clouds, are made of water ice; ice crystals reflect the setting sun, allowing the detail in each cloud to be seen more easily.

Sunset sun rays, Curiosity (March 2023)

https://photojournal.jpl.nasa.gov/catalog/PIA25739

NASA’s Curiosity Mars rover captured these “sun rays” shining through clouds at sunset on Feb. 2, 2023, the 3,730th Martian day, or sol, of the mission. It was the first time that sun rays, also known as crepuscular rays, have been viewed so clearly on Mars. Crepuscular is taken from the Latin word for “twilight”, as these rays appear near sunset or sunrise.

These clouds were captured as part of a follow-on imaging campaign to study noctilucent, or "night-shining" clouds, which started in 2021. While most Martian clouds hover no more than 37 miles (60 kilometers) above the ground and are composed of water ice, these clouds appear to be higher in elevation, where it’s very cold. That suggests these clouds are made of carbon dioxide, or dry ice.

This scene made up of 28 individual images captured by the rover’s Mast Camera, or Mastcam. The images have been processed to emphasize the highlights.

InSight, end of mission

https://photojournal.jpl.nasa.gov/catalog/PIA25680

This is one of the last images ever taken by NASA’s InSight Mars lander. Captured on Dec. 11, 2022, the 1,436th Martian day, or sol, of the mission, it shows InSight’s seismometer on the Red Planet’s surface.

Note the patchy clouds on the background, a pattern spotted also in other situations in the polar regions in the dust storms season. This gives a much better idea of “how the sky normally looks” from the ground vs from orbit, and it’s a nice example of an image which might not be too accurate, but it’s also not enhanced on purpose to show the clouds (to my knowledge at least).

https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Martian_dust_storms_churn_up_Earth-like_clouds ( backup) source: https://www.sciencedirect.com/science/article/pii/S0019103522002846 ( backup )

Martian morning water ice clouds above Valles Marineris seen by Viking Orbiter 1 (1976)

https://photojournal.jpl.nasa.gov/catalog/PIA17940

No NASA Mars orbiter has been in a position to observe morning daylight on Mars since the twin Viking orbiters of the 1970s. This image, taken by Viking Orbiter 1 on Aug. 17, 1976, shows water-ice clouds in the Valles Marineris area of equatorial Mars during local morning time. North is to the upper right, and the scene is about 600 miles (about 1,000 kilometers) across.

Noctis Labyrinthus, morning fog (2001) (North is top-right)

https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_keeps_an_eye_on_curious_cloud

As the sun rises over Noctis Labyrinthus (the labyrinth of the night), bright clouds of water ice can be observed in and around the tributary canyons of this high plateau region of Mars. This color composite image, reconstructed through violet, green, and orange filters, vividly shows the distribution of clouds against the rust colored background of this Martian desert.

The picture was reconstructed by JPL’s Image Processing Laboratory using in-flight calibration data to correct the color balance.

Scientists have puzzled why the clouds cling to the canyon areas and, only in certain areas, spill over onto the plateau surface. One possibility is that water which condensed during the previous afternoon in shaded eastern facing slopes of the canyon floor is vaporized as the early morning sun falls on those same slopes. The area covered is about 10,000 square kilometers (4000 square miles), centered at 9 degrees South, 95 degrees West, and the large partial crater at lower right is Oudemans. The picture was taken on Viking Orbiter 1’s 40th orbit.

More on mesospheric clouds can be found in Kleinböhl, A., “Clouds in the Middle Atmosphere of Mars”, in Reimuller, J. D. (ed.), Project PoSSUM – Polar Suborbital Science in the Upper Mesosphere, Integrated Spaceflight. ã 2017. (https://drive.google.com/file/d/12Fxmt85hPuFjR0GPohiMupl_Ekpp_Gdx/view, backup )

Here some interesting paragraphs.

Clouds in the martian atmosphere can be made of water ice or carbon dioxide ice. The latter do not have an equivalent on Earth as temperatures are never low enough for carbon dioxide to freeze. In addition, carbon dioxide is the main constituent of the martian atmosphere so freezing it out (either due to cloud formation or direct deposition to the surface at the winter poles) has a profound impact on the atmospheric pressure cycle and leads to significant pressure variations over the seasons.

Water ice clouds are omnipresent on Mars. Temperatures are typically suitable for the formation of ice clouds and cloud formation mainly depends on the availability of water vapor. On Earth the tropopause provides an effective cold trap for water vapor, leading to very dry conditions in the stratosphere and mesosphere. On Mars the smaller lapse rate in the atmosphere does not provide an effective cold trap for water vapor, and water ice clouds can form in the lower atmosphere as well as in the middle atmosphere.

The most prominent cloud feature in the lower atmosphere is the aphelion cloud belt, which was already observed from Earth-based measurements. It is a band of clouds that appears in the equatorial region in the northern spring and summer season. Its typical extend is from about 10°S to 30°N in latitude and the clouds reach up to altitudes of roughly 40 km. The aphelion cloud belt is fed by water vapor coming off the north polar cap in spring and summer. The cooler global temperatures during the aphelion season cause clouds to form in the equatorial region. As the perihelion season approaches, the aphelion cloud belt starts to dissipate due to the rising global temperatures. This corresponds to northern fall. Temperatures drop in the northern high latitudes, causing condensation of water vapor in the lower atmosphere of the polar region that leads to the formation of the northern polar hood cloud.

With an extent from the north pole down to 50°N latitude it covers not only the polar region but reaches well into the mid-latitudes. It starts forming in late northern summer around Ls=160° and dissipates again in early northern spring around Ls=20°. The southern polar region also develops a polar hood cloud in southern fall and winter. However, the southern polar water ice clouds are not nearly as dense or as extended as their counterpart in the north. They are present between about Ls=20° and Ls=180°, with a notable gap in occurrence between Ls=70° and Ls=110°.

Like the northern polar hood, also the southern polar hood is constrained to the lower atmosphere. However, in contrast to the north, the southern polar hood cloud is shaped like an annulus, mostly covering the latitudes between 60°S and 80°S. […]

The most prominent feature of Figure 2 is a cloud in the equatorial region.

This is not during the season of the aphelion cloud belt. However, a temperature minimum at 30-50 km altitude between about 10°S and 40°N causes water vapor to condense and form a cloud. In addition, temperature minima at higher altitudes to the south (40°S-10°S) and to the north (40°N-60°N) lead to cloud formation. Water ice clouds in these regions are found at altitudes of 60-70 km in the middle atmosphere. This shows that at least in this season, water vapor can penetrate high enough into the atmosphere to allow the formation of water ice clouds in the middle atmosphere.

[…] In the previous section it was shown that water ice clouds on Mars can reach mesospheric altitudes. This happens predominantly in the perihelion season (Ls=180°-360°) when the atmosphere is dustier and lower atmospheric temperatures are higher, allowing the transport of water vapor to higher altitudes of the atmosphere.

However, parts of the martian atmosphere can become cold enough to allow carbon dioxide to condense, leading to the formation of CO2 ice clouds. A feature that makes this process particularly intriguing is that CO2 is the main constituent of the martian atmosphere. In the lower atmosphere of the polar regions, temperatures in winter regularly drop to values at which CO2 condenses. The condensation of CO2 is the main driver of the seasonally varying surface pressure on Mars. In Figure 2, temperatures drop below the frost point of CO2 ( 145 K at martian pressures in the lower atmosphere) in the center of the vortex close to the pole. Hence the conditions in these regions are favorable for the formation of lower atmospheric CO2 ice clouds. Due to the high abundance of CO2 in the martian atmosphere, these clouds are expected to grow to large particle sizes rather quickly, causing CO2 snowfall in the winter polar region. Observations of high clouds or detached aerosol layers in the aphelion season raised the question whether the martian mesosphere could also become cold enough to allow atmospheric CO2 to condense and form mesospheric clouds.

Observations of high clouds or detached aerosol layers in the aphelion season raised the question whether the martian mesosphere could also become cold enough to allow atmospheric CO2 to condense and form mesospheric clouds. […] Since the 2000s, observations by instruments on several Mars orbiters including Mars Global Surveyor (MGS), Mars Express (MEx), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO) have been providing a multitude of evidence of martian middle atmospheric CO2 clouds. […]

One of the main drivers of temperature variations in the martian atmosphere are atmospheric tides. Tides are periodic changes in atmospheric parameters like temperature, pressure, and wind that have periods of a fraction of a solar day. They are driven by the changes of solar energy input to the Mars surface and atmosphere over the course of a day. This is in contrast to ocean tides on Earth that are driven by the gravitational pull of the moon and the sun.

Due to the thin atmosphere on Mars, most of the solar radiation reaches the surface, where it causes strong differences in temperature between day and night. Surface temperature maxima are typically reached at local noon or slightly later, while surface temperature minima are reached in the early morning. The heat flux from the surface causes changes in pressure and temperature in the lowermost atmosphere.

The propagation of these changes gives rise to global oscillations in atmospheric pressure and temperature, and subsequently also wind. The most prominent oscillation is the diurnal tide, which has a period of one solar day, meaning that for example temperature will exhibit one minimum as well as one maximum over the course of a day. While thermal tides also exist on Earth, their temperature perturbations typically start to become significant only at altitudes of the upper mesosphere and above. On Mars, thermal tides cause significant temperature variations throughout the atmosphere. […]

The right panels of Figure 7 show the occurrence of water ice clouds as observed by MCS, separated for day and night. Few water ice clouds are observed above 50 km altitude in this season. The only notable cloud occurrence in the upper middle atmosphere is observed at 60°-70°S around 70 km altitude, coincident with very low temperatures found in this region. Elsewhere water ice clouds mainly from in locations consistent with temperature minima driven by the diurnal tide. At nighttime, clouds tend to from close to the surface and around 40 km altitude in the equatorial region. At daytime the pattern reverses and clouds tend to form predominantly between 20 and 30 km altitude, where the equatorial daytime temperatures are lower than at night.

The formation of water ice clouds is very common at temperatures found in the martian atmosphere and limited largely by the availability of water vapor. During aphelion season, water vapor in the middle atmosphere is limited by the extensive cloud formation below 40-50 km such that water ice clouds at mesospheric altitudes are rare. During perihelion season (southern spring and summer) the warmer and dustier lower atmosphere allows water vapor to be transported to higher altitudes, enabling the frequent formation of water ice clouds. Small dust particles, advected together with water vapor to mesospheric altitudes, could serve as nuclei for cloud condensation.

The presence of clouds at altitudes of 50-70 km in perihelion season (Figure 2) indicates localized water vapor mixing ratios of tens of ppm, which would be about an order of magnitude higher than in Earth’s stratosphere and mesosphere.

Recurrent clouds #

Martian weather seems to be quite predictable.

Mars Orbiter Camera data beginning in March 1999 and covering 2.5 Martian years show that Martian weather tends to be more repeatable and hence more predictable than that of Earth. If an event occurs at a particular time of year in one year, the available data (sparse as it is) indicates that it is fairly likely to repeat the next year at nearly the same location, give or take a week.

Some evident examples from the Tharsis region:

https://www.jpl.nasa.gov/images/pia04294-repeated-clouds-over-arsia-mons

Some parts of Mars experience weather phenomena that repeat each year at about the same time. In some regions, the repeated event may be a dust storm that appears every year, like clockwork, in such a way that we can only wish the weather were so predictable on Earth. One of the repeated weather phenomena occurs each year near the start of southern winter over Arsia Mons, which is located near 9 degrees south latitude, 121 degrees west longitude. Just before southern winter begins, sunlight warms the air on the slopes of the volcano. This air rises, bringing small amounts of dust with it. Eventually, the rising air converges over the volcano’s caldera, the large, circular depression at its summit. The fine sediment blown up from the volcano’s slopes coalesces into a spiraling cloud of dust that is thick enough to actually observe from orbit.

The spiral dust cloud over Arsia Mons repeats each year, but observations and computer calculations indicate it can only form during a short period of time each year. Similar spiral clouds have not been seen over the other large Tharsis volcanoes, but other types of clouds have been seen.

The spiral dust cloud over Arsia Mons can tower 15 to 30 kilometers (9 to 19 miles) above the volcano. The white and bluish areas in the images are thin clouds of water ice. In the 2005 case, more water ice was present than in the previous years at the time the pictures were obtained. For scale, the caldera of Arsia Mons is about 110 kilometers (68 miles) across, and the summit of the volcano stands about 10 kilometers (6 miles) above its surrounding plains.

https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_keeps_an_eye_on_curious_cloud

In spite of its location, this atmospheric feature is not linked to volcanic activity but is rather a water ice cloud driven by the influence of the volcano’s leeward slope on the air flow – something that scientists call an orographic or lee cloud – and a regular phenomenon in this region. The cloud can be seen in this view taken on 10 October by the Visual Monitoring Camera (VMC) on Mars Express – which has imaged it hundreds of times over the past few weeks – as the white, elongated feature extending 1500 km westward of Arsia Mons. As a comparison, the cone-shaped volcano has a diameter of about 250 km […] Mars just experienced its northern hemisphere winter solstice on 16 October. In the months leading up to the solstice, most cloud activity disappears over big volcanoes like Arsia Mons; its summit is covered with clouds throughout the rest of the martian year. However, a seasonally recurrent water ice cloud, like the one shown in this image, is known to form along the southwest flank of this volcano – it was previously observed by Mars Express and other missions in 2009, 2012 and 2015.

The cloud’s appearance varies throughout the martian day, growing in length during local morning downwind of the volcano, almost parallel to the equator, and reaching such an impressive size that could make it visible even to telescopes on Earth. The formation of water ice clouds is sensitive to the amount of dust present in the atmosphere. These images, obtained after the major dust storm that engulfed the entire planet in June and July, will provide important information on the effect of dust on the cloud development and on its variability throughout the year.

The elongated cloud hovering near Arsia Mons this year was also observed with the visible and near-infrared mapping spectrometer, OMEGA, and the High Resolution Stereo Camera (HRSC) on Mars Express, providing scientists with a variety of different data to study this phenomenon.

Potential colonies #

Calculations #

Circumnavigation of Mars #

Assuming the Earthly speed of a glider to be around 200km/h, how long would it take at this speed to circumnavigate Mars?

6600km * 6.28 / 200km/h / 24h = 8.6 days

However there are tons of issues using the Earthly speed of a glider as a reference for reasonable gliding speeds on Mars. See Fixed-wing flight for the reasoning.