Here on Earth, we can have some pretty immense dust storms. Some of them can even be seen from space. But a storm that completely envelopes our planet? That would take an extremely unusual and mammoth weather event.
On Mars, though, things can swirl out of control much easier. A runaway series of smaller dust storms can occasionally domino into a world-covering event, a dust cloud that completely veils the planet. In fact, the Red Planet experiences one of these windfall events about every six to eight years. And right now is one of those times, reports Phys.org.
A before and after photo (shown above) taken by NASA's Mars Reconnaissance Orbiter shows just how dramatically these storms can encompass the planet. The storm, which reached its height in June, is also wreaking havoc on our ability to monitor conditions on Mars from both space and on the ground. For instance, the Opportunity rover, which runs on solar power, had to be shut down until the storm passes, which could take months. And even then, Opportunity could be compromised by the dust that is bound to settle over its panels.
This series of images shows simulated views of a darkening Martian sky blotting out the sun from NASA’s Opportunity rover’s point of view, with the right side simulating Opportunity’s view in the global dust storm (June 2018). The left starts with a blindingly bright mid-afternoon sky, with the sun appearing bigger because of brightness. The right shows the sun so obscured by dust it looks like a pinprick. (Photo: NASA/JPL-Caltech/TAMU)
This leaves the Curiosity rover, which runs on nuclear power, as our only eyes left beneath the shroud. Using Curiosity's THEMIS instrument (Thermal Emission Imaging System), scientists can track Mars' surface temperature, atmospheric temperature, and the amount of dust in the atmosphere. So even though we're handicapped to a single point of view, we can at least watch the dust storm grow and evolve from the inside, and that's proving to be extremely valuable.
"The very fact that you can start with something that's a local storm, no bigger than a small [U.S.] state, and then trigger something that raises more dust and produces a haze that covers almost the entire planet is remarkable," said Rich Zurek of NASA's Jet Propulsion Laboratory.
What we can learn from the storms
Scientists are hoping they can begin to unravel the mystery of how these global storms get triggered on Mars, as well as test some theories about whether dust storms like these might explain what happened to the water that was once more plentiful on the planet's surface.
For instance, we know that at some point billions of years ago, Mars' atmosphere must have been thicker and more insulating, similar to Earth's, which would have allowed liquid water to pool. But as storms like the one going on now carry more water vapor high into the atmosphere, more of it is broken down by sunlight, and hydrogen atoms might then get exposed to the solar wind and get swept into space.
So while these storms limit our view of Mars, they are also special events with the power to reveal rare clues about the planet's evolution. The science never stops. It's worth thinking about when you catch that glint of orange in the night sky over the next couple of months.