These models draw on familiar physics equations known on Earth but contain tweaks for gravity, rotational speed or atmospheric pressure, for instance.
But by leveraging the sheer amount of knowledge and data about our planet, scientists can get a head start on understanding the inner workings of storms or vortexes on other planetary bodies.
In some cases, the models provide almost everything we know about some otherworldly atmospheric processes.
“Our planetary atmosphere models are derived almost exclusively from these Earth models,” said Scot Rafkin, a planetary meteorologist at the Southwest Research Institute. “Studying the weather on other planets helps us with Earth and vice versa.”
Vortexes on Jupiter
If you looked at the churning clouds near Jupiter’s pole, they appear like ocean currents on Earth – as if you’re looking at small edges and meandering fronts in the Baltic Sea.
“This looks so much like turbulence I’m seeing in our own ocean. They must be covered by at least some similar dynamics,” Lia Siegelman, a physical oceanographer at Scripps Institution of Oceanography, recalled the first time she saw images of vortexes from Nasa’s Juno mission, which entered Jupiter’s orbit in 2016.
Working with planetary scientists, she applied her understanding of the ocean physics on Earth to the gas giant in computer models. Whether it’s in air or water on any planet, she found the laws of physics that govern turbulent fluids is the same (even though the vortex on Jupiter is about 10 times larger than one on Earth).
When cyclones and anticyclones (which spin in the opposite direction) interact in the ocean, they create a boundary of different water masses and characteristics – known as a front. She and her colleagues found the same phenomenon occurs in cyclones at Jupiter’s poles, showing similar swirls.
“By studying convection on Earth, we were also able to spot that phenomenon occurring on Jupiter,” Siegelman said, even though Jupiter has relatively little data compared to Earth.
She and her colleagues also found a pattern never seen on Earth before: a cluster of cyclones in a symmetrical, repeating pattern near the poles of Jupiter. These “polar vortex crystals” were observed in 2016 and have remained in place since.
Despite never seeing them on Earth, she and other planetary scientists collaborated to reproduce these swirls in computer models – relying on “just very simple physics”.
“Planetary scientists use a lot of the weather models that have been developed to study either the ocean or the atmosphere,” Siegelman said. “By just knowing so much about the ocean and the atmosphere, we can just guide our analysis.”
Dust storms on Mars
If you plan to move to Mars, be prepared to face the dust storms.
At their most intense, they can engulf the entire planet and last from days to months. The dirt can block sunlight and coat infrastructure. While scientists have observed many of these storms, they still don’t know how to predict them.
Dust storms operate similarly on Earth and Mars. Dust is lifted and heated and rises like a hot-air balloon, Rafkin said.
The rising air will suck in air from below to replace it. Air pressure drops near the surface, sucking in more wind that lifts the dust. As Mars spins, the angular momentum causes the dust storm to rotate.
In reality, Martian dust storms are more similar to hurricanes on Earth in terms of their scale and circulation, said planetary scientist Claire Newman. She said the sources are different (Mars is a dust planet, whereas Earth is a water planet), but they have a similar effect on temperature and winds.
But it’s still unknown how these Martian dust storms form. On Earth, a winter storm with a cold front can lift the dust; scientists sometimes see similar dust lifting along cold fronts on Mars, but many storms just seem to pop up.
To predict a dust storm, scientists need to understand the circulation patterns on Mars – forecasting the cold front that can lift the dust, for instance. But it’s something researchers don’t yet understand.
Wind measurements are scarce on Mars, aside from a few scattered measurement sites on its surface. With adjustments, Earth-based models can simulate the conditions that can lead to the uplifting winds and dust storms.
“Almost everything that we know about the circulation patterns on Mars come from models,” said Rafkin, adding that scientists “have effectively no observations of the movement of the air on Mars”.
The models currently serve as the best way to understand dust storms on the Red Planet, unless more dedicated studies and stations are added, similar to Earth.
“We’re basically applying these models to try and get a sense of what the environment is,” said Newman, “before we send robots or potentially people there”.
Rain on Titan
The second-largest moon in our solar system, Titan is the only other known world besides Earth that has standing bodies of rivers, lakes and seas on its surface – consisting of liquid methane instead of water.
That’s partly why some scientists think it could be a future home for Earthlings, if we can just figure out the 1210 million km journey and learn how to survive the -179C surface temperatures.
But how did those lakes and oceans fill up? Even though it rains methane, the precipitation on Titan is very similar to that on Earth, Rafkin said.
On Earth, take a chunk of air with water vapour, cool it off and the air becomes saturated to form a cloud. Those small cloud droplets can bump into one another or take in more water vapour to grow bigger. But eventually, the water vapour starts to condense into a liquid and brings rain.
We’ve seen this process take place on Earth both naturally in the atmosphere and in labs enough times to understand the physics.
But limited observations on Titan – effectively only visiting its atmosphere a handful of times – have caused scientists to turn to models.
Using the same underlying physics, scientists can model the cloud-making process on this foreign body. And, the modelled clouds look a lot like the few they have observed in real life on Titan.
“If we try to model them and we get clouds, but they look totally bizarre and different than what we’re observing, then that’s an indication that maybe we’re not representing the cloud processes correctly,” Rafkin said.
“But as it turns out, for the most part, when we model these things, we can produce clouds that look reasonably close to what we’ve observed.”
Because of its incredibly dense atmosphere, Titan has stormclouds – two to four times taller than those on Earth – that are able to produce feet of methane rain.
While scientists haven’t observed such huge volumes, they have modelled the deluges based on the surface darkening as a storm passed – similar to how rain on soil or pavement darkens the surface on Earth.
It’s still a mystery where the methane comes from. But at least we know to bring a very, very sturdy raincoat if we ever visit Titan.
