July 14, 2024
1 Solar System Way, Planet Earth, USA
Solar System

Large dust storms on Mars

Large dust storms on Mars

Two 2001 images taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance as haze kicked up by dust storm activity in the south became distributed globally.

On the left, an image from late June 2001 shows clear conditions over much of the planet, with regional dust storm activity in the Hellas Basin (bright oval shape) near the edge of the southern polar cap. On the right, a July 2001 image from the same perspective shows the planet almost completely enveloped. Dust spreads to altitudes of more than 60 kilometers (37 miles) during global-scale storms.

Although dust storms occur year-round on Mars, they often occur in greater numbers during certain seasons. In particular, it has long been known, thanks to telescopic observations from Earth, that the largest global dust events (those that envelop the entire planet) occur during the southern spring and summer. When the Mars Global Surveyor (MGS) mission began monitoring this period for the second time, special attention was paid to local and regional dust storms in anticipation of capturing, for the first time, high spatial and temporal resolution observations of the onset of a “global” storm.

Throughout June 2001, the MGS Mars Orbiter Camera (MOC) routinely accumulated low-resolution (7.5 km/pixel) global maps of Mars, orbit by orbit. A moderately large number of local dust storms were observed, especially along the retreating margin of the seasonal south polar CO2 ice sheet and around the large, deep Hellas impact basin dominating the southern highlands. and from the east. On June 21, a small, otherwise indistinguishable dust storm moved into the basin from the southwest. When seen 24 hours later, the storm had circulated clockwise about 1/3 of the circumference of Hellas, indicating relatively strong winds. Over the next three days, this storm developed north of Hellas and east toward Hesperia, but did not cross the equator. Then, sometime between 2:00 pm Mars local time on June 25 and 2:00 pm Mars local time on June 26, the storm exploded northward across the equator, and Less than 24 hours later, dust was rising from locations in Arabia, Nilosyrtis, and Hesperia, thousands of miles from Hellas. This was the beginning of the long-awaited global dust event.

Over the following week, dust injected high in the stratosphere during the initial storms Hellas and Hesperia drifted eastward, carried by the predominant southern circumpolar jet stream. Beneath this “veil” of dust, an intense wind front crossed Mars, creating the conditions for many other local and regional dust storms. On July 4, a large regional storm was sweeping between Daedalia Planitia south of the Tharsis and Syria Planum volcanoes (just south of Labyrinthus Noctis). Another storm raised plumes of dust in north-central Noachis and southwestern Meridiani. Columns of smoke rose in Hesperia, but not in Hellas.

Throughout July and August, MOC observations revealed a general pattern of regional storm centers beneath an ever-expanding veil of stratospheric dust. The Daedalia/Claritas/Syria storm generated plumes of dust for more than 90 consecutive days.

Previous views and perceptions of global dust events had noted regional glows within the overall blanket of what was called a “global dust storm.” From our new observations, we know that at least this global dust “storm” was actually a set of storms, somehow triggered to occur at the same time. We also know that during this global event dust did not rise from everywhere on the surface, but rather from discrete, long-lived centers of activity. We saw, for the first time, a rapid, trans-equatorial flow of dust-raising winds.

Image credit: NASA/JPL/MSSS
Explanation from: https://photojournal.jpl.nasa.gov/catalog/pia03170

    Leave feedback about this

    • Quality
    • Price
    • Service

    PROS

    +
    Add Field

    CONS

    +
    Add Field
    Choose Image
    Choose Video
    X