In July 2020, NASA’s Parker Solar Probe was traveling toward the Sun intending to get as close to our star as any human artifact has ever been. His route included passing close to Venus and, taking advantage of the moment, he captured some stunning views of our cosmic neighbor. It was no accident. The second planet in the Solar System plays a critical role in the mission the spacecraft is scheduled to ‘brush’ Venus up to seven times over seven years, gradually reducing its elliptical orbit around the Sun and studying its mysteries. But, along with the orbital dynamics, it is planned that during these ‘visits’ the Parker Solar Probe will take images of the planet that may even reveal some secrets of the inner Solar System. The photograph that NASA has now made public is a snapshot taken during the third gravitational assist of Venus on July 11, at which time the WISPR instrument photographed the night side of the planet at a distance of 12,380 kilometers.

What can be seen in the image, Although WISPR is designed to image the solar corona and heliosphere, as well as the solar wind and its structures, on Venus it detected a bright edge that may be a night glow – light emitted by oxygen atoms high in the atmosphere that they recombine into molecules on the night side. On the other hand, bright streaks are usually caused by a combination of charged particles, called cosmic rays, sunlight reflected by grains of space dust, and particles of material ejected from spacecraft structures after impact with those dust grains. The number of stripes varies throughout the orbit or when the spacecraft travels at different speeds, and scientists are still arguing about the specific origins of the stripes here. Finally, and most incredible, you can see a dark spot in the center of the image that corresponds to Aphrodite Terra, the largest mountainous region on the surface of Venus. “The reason that it appears darkened is that its temperature (about 30 degrees Celsius) is lower than that of the rest of its environment,” a report from NASA.

Surprises behind the photo

This feature took the team by surprise: “WISPR is designed and tested for visible-light observations. We expected to see clouds, but the camera looked directly at the surface, “says Angelos Vourlidas, a WISPR project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. WISPR captured thermal emission from the surface of Venus,” said Brian Wood, an astrophysicist and a member of the WISPR team at the US Naval Research Laboratory in Washington. “It is very similar to the images taken by the Akatsuki spacecraft at near-infrared wavelengths.” The Japanese space agency JAXA’s mission, PLANET-C (also known as Akatsuki), arrived at Venus in 2015 intending to study the neighboring planet’s climate.

How did the Parker probe get to see the surface?

This surprising observation sent the WISPR team back to the lab to measure the instrument’s sensitivity to infrared light. ‘If WISPR can capture wavelengths of near-infrared light, the unforeseen ability would provide new opportunities to study dust around the Sun and in the inner Solar System. But if it cannot do it, then these images, which show characteristics of the surface of Venus, may have revealed an unknown ‘window’ through the atmosphere of the planet, “they say from NASA. “Either way,” Vourlidas says, “some exciting scientific opportunities await us.”

To learn more about the images, the WISPR team planned a set of similar observations of the nightside of Venus during the last flyby on February 20. Scientists on the mission team expect to receive and process that data for analysis in late April. We can’t wait to see these new images,” says Javier Peralta, a planetary scientist on the Akatsuki team, who first suggested a Parker Solar Probe campaign in conjunction with the Akatsuki mission. “If WISPR can sense the thermal emission from the surface of Venus and the night glow, most likely from oxygen, at the edge of the planet it can make valuable contributions to studies of the planet’s surface.