Although its main mission is to look at the Sun, NASA’s Parker Solar Probe will seize any opportunity to send data back to Earth.
The planet Venus represents precisely one of those opportunities, or rather, seven of them. Seven times during its mission, the probe will rotate around Venus for gravity assist, using the planet’s gravity like a slingshot to correct course and speed as it gets closer and closer to the Sun.
The solar probe performed the third of these maneuvers on July 11, 2020, and as it got closer it took a glamorous photo of the night side of the planet using the Wide-field Imager for Parker Solar Probe (WISPR) instrument.
Parker isn’t the only probe taking pictures of Venus as it makes its way through the inner Solar System. BepiColombo, a joint Mercury probe of the European and Japanese space agency, took a video of Venus as it performed a gravity assist maneuver last year.
Those images show the planet relatively smooth and featureless. That’s not entirely surprising: Venus is shrouded in a thick, toxic atmosphere with mostly sulfuric acid clouds that reflect around 70 percent of the light that hits them. This is why Venus is one of the brightest objects in the night sky.
Parker’s team expected to see an orb without similar characteristics, but that’s not what they saw when they processed the WISPR data.
If you look at the image, you can see a bright glow around the edge of the planet. That, the team believes, is a night glow.
This is produced by atoms in the upper atmosphere. On the day side of the planet, solar radiation splits carbon dioxide in the upper atmosphere into oxygen and carbon monoxide. When night falls, the atoms recombine into carbon dioxide, causing a glow.
This is something that also happens on Earth and Mars, and has been seen before on Venus; his presence in Parker’s image is not surprising.
Neither are the white stripes – although Parker’s team isn’t sure what they are, there are a number of candidates, including dust, cosmic rays, material ejected from the spacecraft after being hit by dust, or a combination of all. they.
What is surprising is that dark spot on the face of the planet. That is a region called Aphrodite Terra, the largest mountainous region on the planet’s surface.
WISPR, designed to image the solar corona and coronal ejections, is optimized for visible light observations, but somehow peered through the clouds of Venus.
However, scientists believe they know what happened. Venus is currently on an active mission, the Akatsuki probe of the Japanese Space Agency. Sends similar images, taken with your infrared camera, sensitive to temperature variations.
Aphrodite Terra, at its higher altitude, is much cooler than the surrounding terrain, so in infrared or near-infrared images of the planet, it would be visible.
“WISPR effectively captured thermal emission from the surface of Venus,” said astrophysicist and WISPR team member Brian Wood of the US Naval Research Laboratory. “It is very similar to the images acquired by the Akatsuki spacecraft at near-infrared wavelengths.”
This means that WISPR could be more sensitive to infrared light than it was designed for, which, in turn, opens up new possibilities for Parker’s main mission of studying the Sun. Parker’s team is taking a closer look at the specifications. the instrument to find out exactly what it did.
“Either way,” said WISPR project scientist Angelos Vourlidas of the Johns Hopkins Applied Physics Laboratory, “we have some interesting scientific opportunities ahead of us.”