Last summer, the Parker Solar Probe flew past Venus en route to fly closer to the Sun. In a bit of a surprise, one of the spacecraft cameras, the Wide-field Imager for Parker Solar Probe, or WISPR, captured a striking image of the planet’s night side 12380 km away.
The surprise of the image was that WISPR – a camera with visible light – apparently captured the surface of Venus in infrared light.
Mission scientists expected that WISPR would capture Venus’ thick carbon dioxide clouds, which normally block the surface view. But instead, the camera could see through the clouds and reveal the dark-colored shape of Aphrodite Terra, a highland area near Venus’ equator. The function looks dark due to the lower temperature, about 85 degrees Fahrenheit (30 degrees Celsius) cooler than the environment.
“WISPR has been adapted and tested for observations of visible light,” said Angelos Vourlidas, the WISPR project scientist. “We expected to see clouds, but the camera looked up at the surface.”
While the Parker Solar Probe is the sun, NASA says Venus plays a critical role in the mission. During its seven-year mission, the spacecraft soars past Venus a total of seven times and uses the planet for gravity. This causes the spacecraft to fly ever closer to the sun.
The fly in July 2020 was the third of the seven gravity bystanders.
Credits: NASA / Johns Hopkins APL / Naval Research Laboratory / Guillermo Stenborg and Brendan Gallagher
“WISPR has effectively captured the thermal emission of the Venusian surface,” said Brian Wood, an astrophysicist and WISPR scientist at the U.S. Naval Research Laboratory in Washington, DC. Wood added that the image is similar to that taken by the Japanese Akatsuki spacecraft, which is currently studying Venus, and it contains cameras that can capture light at near-infrared wavelengths.
The bright streaks in the image are usually caused by a combination of charged particles – called cosmic rays – and sunlight reflected by grains of spacecraft, and particles of material shot out of the structures of the spacecraft after the impact on the dust grains. The number of stripes varies across the orbit or when the spacecraft moves at different speeds, and scientists are still discussing the specific origin of the stripes here.
Here’s a look at a “tidy up” version by image-enthusiastic (and former UT author) Jason Major:
WISPR is designed to take pictures of the solar corona and the inner heliosphere in visible light, as well as images of the solar wind and its structures as they approach and fly through the spacecraft. At Venus, the camera detects a bright edge around the edge of the planet, which may be a night glare – light emitted by oxygen atoms high in the atmosphere that reunites into molecules at night.
This surprising observation sent the WISPR team back to the laboratory to measure the instrument’s sensitivity to infrared light.
If WISPR can see it in infrared, it could provide an unexpected new way for the mission to study dust that surrounds the sun. To test this, the WISPR team is planning a set of similar observations of Venus’s night during Parker Solar Probe’s latest Venus flight – which just took place on February 20, 2021. Scientists from the mission team expect to receive and process the data for analysis by the end of April.
But if the appearance of Aphrodite Terra was a kind of ‘fluke’, it could mean that WISPR discovered a previously unknown opening in the thick Venusian clouds, providing a fleeting window showing portions of the planet’s surface.
“Either way,” said Vourlidas, “some exciting scientific opportunities await us.”
Source: NASA