How Webb Will Explore Mars

Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed. Credits: NASA/JPL/MSSS

In the summer of 2018, a dust storm blanketed the entire planet Mars. From the surface, the Sun would have looked like tiny orb in a murky brown sky.

Dust carpeted the solar panels of NASA's intrepid Opportunity rover, which would not recover after it lost power. Orbiting spacecraft and the Curiosity rover monitored the storm from their respective vantage points, but none of these robotic explorers had a view wide enough to see the entire planet at once.

When NASA's James Webb Space Telescope, launching in 2021, reaches its destination a million miles from Earth, it will be able to see the whole disk of Mars every two years. If a global dust storm envelops the Red Planet at a time when Webb could see it, the powerful space telescope could gather information about the storm, adding to data from spacecraft on or close to the planet's surface.

Reporting Martian weather is just one way in which Webb, designed to gaze into deep space and unlock cosmic mysteries, can join forces with other NASA spacecraft to explore Mars. Webb can view Mars in the infrared, a kind of light invisible to human eyes that is especially useful for dissecting certain chemicals in planetary atmospheres. While Webb will primarily look for chemical fingerprints in distant worlds orbiting other stars, exoplanets, it can also use these skills for nearby Mars.

Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed. Credit: NASA/JPL/MSSS

Webb can contribute to key questions about Mars that scientists hope to answer, including: What happened to make the ancient lakes, oceans and rivers on Mars dry up? Could Mars have ever hosted life -- and in the distant or recent past?

"Having another spacecraft with the ability to observe Mars is fantastic, as NASA prepares to send astronauts to the Moon, with an eye on the eventual human exploration of Mars," said Lori Glaze, director of planetary science at NASA.

Webb's ability to sense infrared light makes it well suited to look for certain chemicals that relate to the history of water on Mars. Water is an essential ingredient for life as we know it, so understanding when the planet was wetter is connected to the question any potential life, past or present.




Hydrogen atoms escape from the Mars upper atmosphere, while water containing heavy hydrogen (deuterium) remains trapped on the planet. The escape of hydrogen helped to turn Mars from a wet planet 4.5 billion years ago into a dry world today. Credits: NASA


"Because Webb is an infrared telescope and we have certain sets of filters and instrument capabilities that existing Mars observing satellites don't have, we can provide a different view that's complementary to current assets," said Eric Smith, program scientist for Webb at NASA Headquarters, Washington.

For example, a variant of hydrogen called deuterium is made of one proton and one neutron, and is found in a molecule called "heavy water." Scientists can use Webb to look at Mars' atmosphere and measure the amount of regular water compared to heavy water, a comparison that tells the story of how much regular water has escaped into space. The telescope can map the planet in terms of this comparison and see how it changes over time. These observations will complement those of orbiting spacecraft like the Mars Atmosphere and Volatile Evolution (MAVEN) mission.

Another important chemical Webb can detect that's relevant to Mars' history of habitability is methane. Methane is a gas that is expelled by bacteria on Earth, but is not a surefire sign of life, as geological processes can also create methane. In June 2018, scientists announced that the Curiosity rover had found new evidence for seasonal variations in the levels of methane in the atmosphere of Mars. These variations may stem from interactions between water and rock -- in fact, the rover also found organic molecules, the building blocks of life, in ancient rocks near the surface -- or some other mysterious source. By observing Mars' atmosphere, Webb can be part of the search for clues about Mars' ability to harbor life.

Mars will be part of Webb's Guaranteed Time Observation (GTO) program led by Heidi Hammel, a planetary astronomer and executive vice president of the Association of Universities for Research in Astronomy (AURA) in Washington, D.C.

Still, observing Mars with Webb will not be easy. "Webb is designed to be able to detect extremely faint and distant targets, but Mars is bright and close," said Geronimo Villanueva, Mars scientist at NASA's Goddard Space Flight Center. Mars will appear very bright to Webb, and engineers must carefully design any observations of the planet so that its instruments won't be overexposed to light.

The earliest opportunity Webb will have to look at Mars is in August 2022.

The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

For more information about Webb, visit www.nasa.gov/webb.

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