[meteorite-list] Study Predicts Next Global Dust Storm on Mars

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=6638

Study Predicts Next Global Dust Storm on Mars
Jet Propulsion Laboratory
October 5, 2016

Global dust storms on Mars could soon become more predictable -- which 
would be a boon for future astronauts there -- if the next one follows 
a pattern suggested by those in the past.

A published prediction, based on this pattern, points to Mars experiencing 
a global dust storm in the next few months. "Mars will reach the midpoint 
of its current dust storm season on October 29th of this year. Based on 
the historical pattern we found, we believe it is very likely that a global 
dust storm will begin within a few weeks or months of this date," James 
Shirley, a planetary scientist at NASA's Jet Propulsion Laboratory, Pasadena, 
California.

Local dust storms occur frequently on Mars. These localized storms occasionally 
grow or coalesce to form regional systems, particularly during the southern 
spring and summer, when Mars is closest to the sun. On rare occasions, 
regional storms produce a dust haze that encircles the planet and obscures 
surface features beneath. A few of these events may become truly global 
storms, such as one in 1971 that greeted the first spacecraft to orbit 
Mars, NASA's Mariner 9. Discerning a predictable pattern for which Martian 
years will have planet-encircling or global storms has been a challenge.

The most recent Martian global dust storm occurred in 2007, significantly 
diminishing solar power available to two NASA Mars rovers then active 
halfway around the planet from each other -- Spirit and Opportunity.

"The global dust storm in 2007 was the first major threat to the rovers 
since landing," said JPL's John Callas, project manager for Spirit and 
Opportunity. "We had to take special measures to enable their survival 
for several weeks with little sunlight to keep them powered. Each rover 
powered up only a few minutes each day, enough to warm them up, then shut 
down to the next day without even communicating with Earth. For many days 
during the worst of the storm, the rovers were completely on their own."

Dust storms also will present challenges for astronauts on the Red Planet. 
Although the force of the wind on Mars is not as strong as portrayed in 
an early scene in the movie "The Martian," dust lofted during storms could 
affect electronics and health, as well as the availability of solar energy.

The Red Planet has been observed shrouded by planet-encircling dust nine 
times since 1924, with the five most recent planetary storms detected 
in 1977, 1982, 1994, 2001 and 2007. The actual number of such events is 
no doubt higher. In some of the years when no orbiter was observing Mars 
up close, Mars was poorly positioned for Earth-based telescopic detection 
of dust storms during the Martian season when global storms are most likely.

Shirley's 2015 paper in the journal Icarus reported finding a pattern 
in the occurrence of global dust storms when he factored in a variable 
linked to the orbital motion of Mars. Other planets have an effect on 
the momentum of Mars as it orbits the solar system's center of gravity. 
This effect on momentum varies with a cycle time of about 2.2 years, which 
is longer than the time it takes Mars to complete each orbit: about 1.9 
years. The relationship between these two cycles changes constantly. Shirley 
found that global dust storms tend to occur when the momentum is increasing 
during the first part of the dust storm season. None of the global dust 
storms in the historic record occurred in years when the momentum was 
decreasing during the first part of the dust storm season.

The paper noted that conditions in the current Mars dust-storm season 
are very similar to those for a number of years when global storms occurred 
in the past. Observations of the Martian atmosphere over the next few 
months will test whether the forecast is correct.

Researchers at Malin Space Science Systems, in San Diego, post Mars weather 
reports each week based on observations using the Mars Color Imager camera 
on NASA's Mars Reconnaissance Orbiter. A series of local southern-hemisphere 
storms in late August grew into a major regional dust storm in early September, 
but subsided by mid-month without becoming global. Researchers will be 
closely watching to see what happens with the next regional storm.

News Media Contact
Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster at jpl.nasa.gov

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown at nasa.gov / laura.l.cantillo at nasa.gov

2016-256