Forecasting global dust storms on Mars will be vital for future human missions, says NASA, which believes it will soon be able to predict them, if the next one follows a pattern seen in previous ones. Global dust storms encircle the whole planet.
According to a NASA study, the climatic patterns in the Red Planet point to a global dust storm occurring within the next few months.
James Shirley, a planetary scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California, USA, said:
“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.”
This image shows a similarity between 2016 (dark blue line) and the past five years in which the Red Planet has experienced global dust storms (orange lines and band), compared to years when no global dust storm occured (blue-green lines and band). The horizontal scale is time-of-year on Mars. (Image: mars.nasa.gov)
Local dust storms sometimes coalesce
Mars often has local dust storms which occasionally grow or coalesce to cover whole regions, particularly during the southern summer and spring, when the planet is closest to the Sun.
On very rare occasions, a regional storm can produce a dust haze that encircles the whole planet and obscures Mars’ surface features.
On even rarer occasions, they may turn into truly global storms, such as the 1971 storm that greeted the first spacecraft to orbit the Red Planet – NASA’s Mariner 9.
Scientists say that detecting a predictable pattern for which years there will be global storms – that literally encircle the whole planet – has been challenging.
These two images of Mars, taken in 2001 by the Mars Orbiter Camera on the Mars Global Surveyor orbiter, show how a global storm hides the planet’s surface. The two images were taken about one month apart. (Image: nasa.gov)
Global dust storm undermines solar power generation
The last global dust storm – one that encircled the whole of Mars – occurred in 2007. It significantly reduced solar power available to two NASA Mars rovers – Opportunity and Spirit – which were active at the time and about halfway around the planet from each other.
JPL’s John Callas, Project Manager for Spirit and Opportunity, said:
“The global dust storm in 2007 was the first major threat to the rovers since landing. 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 represent a major challenge for humans on the Red Planet. Even though the wind forces are nowhere near as strong as those portrayed in the movie The Matian, the dust could play havoc with electronic equipment, human health, as well as solar energy generation.
Nine global dust storms since 1924
Since 1924, Mars has been observed encircled by a global dust storm nine times – the last five occurred in 1977, 1982, 2001 and 2007. According to NASA, those are just the ones we have managed to detect, the real number is most likely considerably higher.
NASA wrote:
“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.”
In 2015, Shirley published a paper in Icarus (citation below) where he says he found a pattern in the occurrence of global dust storms when he factored in a variable link to the orbital motion of the Red Planet.
Martian forecast: global dust storm soon. I’ll be OK. Ability to predict = boon for future astronauts #JourneyToMars https://t.co/dZGS98aEq0 pic.twitter.com/jJcDL9IDdx
— Curiosity Rover (@MarsCuriosity) 6 October 2016
Other planets in our Solar System have an effect on Mars’ momentum as it orbits the Sun. This effect on momentum varies with a cycle time span of approximately 2.2 years Earth years – Mars takes 1.9 Earth years to complete one orbit.
The relationship between these two cycles is continuously changing. Shirley discovered that global dust storms tend to take place when the momentum is increasing during the initial part of the dust storm season.
None of the global dust storms observed so far have occurred in years when the momentum was diminishing during the first part of the dust storm season.
The study paper noted that conditions in the current Mars dust-storm season are extremely similar to those for several years when global storms occurred in the past. Observations of the Red Planet’s atmosphere over the next few months will determine whether the forecast is accurate.
Scientists at Malin Space Science Systems in San Diego, California, post Mars weather reports every week based on observations using the Mars Color Imager camera on NASA’s Mars Reconnaissance Orbiter.
A number of local southern-hemisphere dust storms in late August this year grew into a major regional dust storm early in September. However, by the middle of the month they had subsided, and did not become global. Scientists will be closely monitoring Mars’ atmosphere to determine what happens with the next regional storm.
Citation: “Solar System dynamics and global-scale dust storms on Mars,” James H. Shirley. Icarus – Volume 251, 1 May 2015, Pages 128–144. DOI: 10.1016/j.icarus.2014.09.038.
