The Parker Solar Probe has seen a lot of extracurricular activity lately. Originally designed to observe the sun, the probe has made full use of its path through the solar system. In addition to capturing images of comets, the probe has repeatedly focused on Venus, including capturing an image peering beneath the cloud cover of the notoriously hot world. Now, a team led by Glyn Collinson of the Goddard Space Flight Center found another accidental discovery in the data Parker had collected during his last flyby in the summer of 2020 – the probe was actually flying through the upper atmosphere of Venus, and that atmosphere was shining to be different than almost 30 years ago.
Parker used Venus in a gravity maneuver, but not in the traditional way of flinging an object faster into the outer reaches of the solar system. It tries to slow down so it can spend a longer time near the sun, the main objective of its observations. The mission team, which was in the Applied Physics Laboratory at John Hopkins, decided to collect some data. Some of this data resulted in an image under the clouds, while others used a different instrument.
Video describing the FIELDS instrument.
Photo credit: APL YouTube Channel
FIELDS is an instrument that can be used to measure electrical and magnetic fields. It was designed for use in the solar atmosphere, but it also picked up a strange signal during a 7-minute stretch of approach to Venus. In the data, the signal looked like a frown at very low frequencies. In another moment of scientific coincidence, Dr. Collinson remembered where he had previously seen a signal that looked like this.
The same signal could be seen in data from Galileo as it passed through the ionosphere of Jupiter’s moons. Ionospheres are made up of charged plasmas that send out radio waves. But they’re weak enough that Parker had to fly through Venus’ ionosphere to discover them.
Graphics and noise translations of Parker’s interaction with Venus.
Photo credit: NASA Goddard YouTube Channel
This was indeed a coincidence, as no direct measurements of the Venus ionosphere have been made since the Pioneer Venus Orbiter in 1992. This was near a “solar maximum,” the most active period of the sun during its solar cycle. Since then, ground-based observations from Earth have indicated that Venus’ ionosphere has thinned significantly as part of the solar cycle. However, without direct measurements, it was impossible to tell if this actually happened.
These direct measurements are exactly what Parker just provided, and they confirmed the idea that the ionosphere is actually getting thinner, with the reading for 2020 close to a solar minimum. While the thinner ionospheric reading is still tentative and unexplained, confirmation from two different sources is a step to truly understand.
UT video describing the difficulty of exploring Venus.
Parker will soon return to focus on the main subject of his work. But now we can be grateful for the additional science on our sister planet that has emerged from the mission so far. Perhaps there is a chance for more such accidental discoveries later in the mission or with others.
NASA – NASA’s Parker solar probe detects natural radio emission in Venus’ atmosphere
Geophysical Research Letters – Depleted plasma densities in the Venus ionosphere near solar minimum from Parker probe observations of the upper hybrid resonance emission
UT – Parker Solar Probe took pictures of Venus on its way to the sun
UT – Here is the first image of the sun from the Parker Solar Probe
Image Parker peered under the clouds of Venus.
Photo credit: NASA / Johns Hopkins APL / Marine Research Laboratory / Guillermo Stenborg and Brendan Gallagher