by Jim Shelton
Illustration by Michael S. Helfenbein
courtesy of NASA/JPL-Caltech
As scientists prepare for crewed research missions to nearby planets
and moons, they've identified a need for something beyond rovers and
They need accurate weather forecasts. Without them, any trip to the
surface may be one dust storm away from disaster.
A new Yale study (Annular
modes of variability in the atmospheres of Mars and Titan)
helps lay the foundation for more accurate, otherworldly forecasts
by taking a phenomenon related to Earth's jet stream and applying it
to weather patterns on Mars and
Titan, Saturn's largest moon.
The study appears in the
journal Nature Astronomy.
"I believe the first
accurate forecasts of perhaps a few Mars days may be only a
decade away," said lead author J. Michael Battalio, a
postdoctoral researcher in Earth and planetary sciences in
Yale's Faculty of Arts and Sciences.
"It is just a matter
of combining better observational datasets with sufficiently
refined numerical models.
"But until then, we can rely upon connections between the
climate and weather to help anticipate dust storms."
On Earth, the regularity
of storm systems in the middle latitudes is associated with what is
called an annular mode - a variability in atmospheric flow that is
unrelated to the cycle of seasons.
affect the jet stream, precipitation, and cloud formations across
They explain up to
one-third of the variability in wind-driven "eddies," including
blizzards in New England and severe storm outbreaks in the Midwest.
After noticing that the regularity of dust storms in the Southern
Hemisphere of Mars was similar to the repeatability of Earth's
eddies, J. Michael Battalio conceived of the new study.
looking at 15 years of Mars atmospheric observations in a public
dataset, he discovered that Mars also has annular modes, just as
Battalio's lab supervisor,
Juan Lora, an assistant
professor of Earth and planetary sciences at Yale, suggested that
they also look for annular modes on Titan.
Although there are very
few atmospheric observations for Titan, Lora has developed a highly
regarded global climate model for the moon called the Titan
Atmospheric Model (TAM).
Indeed, Battalio and Lora found that annular modes are also
prominent in their Titan simulations.
In fact, the researchers
found that annular modes on Titan - and on Mars - are even more
influential than they are on Earth.
They appear to be
responsible for up to half of the wind variability on Mars and
two-thirds of the wind variability on Titan.
"Methane clouds and
surface changes caused by methane rain on Titan have been
observed before," said Lora, who is co-author of the study.
"And now it seems
these events are connected to shifts of Titan's strong jet
stream, influenced by its annular modes."
"The fact that we
have found annular modes on worlds as different from Earth as
Mars and Titan also means they may be ubiquitous in planetary
atmospheres, from Venus, to the gas giants or exoplanets."
As for Mars, its dust
storms range from tiny dust devils that are constantly occurring to
global dust storms that encircle the planet once every few years.
The smaller storms last
less than a day, but the global events may last months.
There are also regional
events that last days to weeks.
predicting these events is vital for the safety of missions,
particularly those that rely on solar power, but also for all
missions as they land on the surface," Battalio said.
regional events, the dust can become so thick at times as to
make day seem as dark as the middle of the night. Even without a
large, dramatic event, regional storms are a periodic feature."
It is this periodic
nature, researchers said, that could allow for annular modes to
predict dust storms.
Mars, Titan, and Earth's
modes each occur regularly.
Because the annular
modes impact the eddies that cause dust storms, real-time
analysis of the annular modes enables simple predictions of dust
storms without having to rely on a complex model.
robotic rover landed on Mars in 2004 for a 90-day mission; it
operated for more than 14 years, partly by hibernating during dust
Exploration using Seismic Investigations, Geodesy and Heat Transport
robotic lander arrived on Mars in 2018.
"A global event is
what finally ended the Opportunity rover, but the slow
accumulation of dust is currently endangering the survival of
the InSight mission," Battalio said.