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Venus is so hot that its surface visibly shines through its thick clouds at night.
Photos taken by NASA’s Parker Space Probe revealed this.
The planet’s average temperature hovers around 860 degrees Fahrenheit, and thick clouds of sulfuric acid obscure view. So far, the only photos of the Venusian surface have been taken by four Soviet spacecraft that successfully landed there in the 1970s and 1980s and operated shortly before succumbing to the hellish environment.
During their pass by Venus, Parker aimed the spacecraft’s cameras at the night side of Venus. He was able to see visible wavelengths of light, including near-infrared reddish colors that could pass through clouds.
“This is a new way of looking at Venus that we’ve never tried before—in fact, we weren’t even sure it was possible,” said Lori Glaze, director of NASA’s planets division.
Warmer places, such as the low volcanic plains, appeared brighter in the Parker photographs, while those at higher altitudes such as Aphrodite Terra, one of three continent-sized regions on Venus, were about 85 degrees cooler and darker.
“It’s like you’re heating a piece of iron,” said Brian Wood, a physicist at the Naval Research Laboratory in Washington, DC. A study published this month in Geophysical Research Letters explained these findings. “It’s starting to glow a little at very red wavelengths. And what we’re seeing is that the surface of Venus glows in very red wavelengths because it’s very hot.”
The photos also showed a glowing halo of oxygen in the atmosphere.
“We were able to take these really beautiful, stunning images,” said Nicola Fox, director of NASA’s heliophysics division.
Dr. For Wood and other scientists working on the mission, the research was a crash course in planetary science. Dr. “I’ve never studied planets,” Wood said. “We’re all solar physicists. We’re experts in the sun, not the planets.”
As the name suggests, the Parker Solar Probe’s mission is to probe the sun as it defies scorching temperatures as it plunges into the sun’s outer atmosphere. By design, the Parker spacecraft’s orbit makes several close flybys of Venus and uses the planet’s gravity as a brake to keep it closer to the sun.
Known as the Wide Field Imager or WISPR for the Parker Solar Probe, the single-camera device is not designed to look directly at the sun, which is particularly bright at close range. Rather, WISPR looks sideways in charged particles known as the solar wind, which are emitted from the sun at a million miles per hour.
Prior to the release of the Parker Solar Probe in 2018, project scientist for the mission, Dr. Glaze and Dr. Fox discussed the possibility of turning on the instruments during their Venus flyby. However, no definitive plans were made until after launch, and the Parker Space Probe was operating smoothly.
Dr. “This was just because of security concerns,” Fox said. “You don’t really know how your spacecraft is flying until you get into orbit.”
Designed to capture dim solar wind particles, WISPR was adept at revealing the faint glow on the night side of Venus.
It took some trial and error to figure this out. In July 2020, during the first flyby of the camera, scientists discovered that if any part of Venus’ daytime side was in view, the picture was overexposed.
Dr. “We didn’t really know what we were doing,” Wood said. “We quickly learned that this resulted in a completely unusable image.”
But there were only two images of the night side. Dr. “These are images that tell us, ‘Wow, okay, so now we’re seeing something,'” Wood said.
Scientists were better prepared when the spacecraft made another flight last February, capturing enough images to put together in one movie.
Other orbiting spacecraft, including Japan’s Akatsuki and the European Space Agency’s Venus Express, have observed similar patterns at longer infrared wavelengths invisible to the human eye. (Dr. Wood said it’s unclear whether an astronaut orbiting above the night side of Venus would be able to see the glow Parker detected, because the human eye can barely detect these wavelengths.)
Because different materials glow at different intensities at different wavelengths, it may be possible to combine Parker data with infrared observations from other spacecraft to help identify certain minerals on the surface.
Dr. “This is where we want to go with this data, but we haven’t gotten that far yet,” Wood said.
The data will also help NASA’s future Venus missions, such as DAVINCI+, which will launch at the end of the decade and send a parachuted probe to the surface. “I think it will It’s a really exciting time,” said DAVINCI+ principal investigator James Garvin. “Venus will come alive.”
The Parker Space Probe won’t get a better look at the night side of Venus until its final flyby in November 2024.
Dr. Wood noted a historical symmetry to Venus findings. In 1962, the first successful interplanetary probe, NASA’s Mariner 2 mission to Venus, confirmed the existence of the solar wind. This was a prediction by astrophysicist Eugene Parker, whose task is of the same name as the task he is currently working on.
Dr. “I find it fascinating that this link between Venus research and solar wind research has existed from the very beginning,” Wood said.
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