The Parker spacecraft was launched several years ago to study the sun, and that remains its primary mission. However, the solar probe has also made some close passes of the inner planets. A new study reveals that Parker got so close to Venus that it picked up a natural radar ping, proving it passed through the planet’s upper atmosphere. This is the first direct measurement of Venus’s atmosphere in decades, and it looks much different than the last time.
Depending on your frame of reference, the Parker Solar Probe is already the fastest spacecraft ever launched, and it’s getting faster with each gravity assist. It was during one of these gravity assists in July 2020 when the vessel passed just 517 miles (833 km) above the planet’s surface. For seven minutes during its flyby, Parker’s FIELDS instrument detected a natural, low-frequency signal. Glyn Collison of NASA’s Goddard Space Flight Center quickly realized what they had, drawing on his work on the Galileo orbiter. That mission detected a similar radio hum each time it skimmed the atmosphere of Jupiter’s moons.
Venus and Earth are very similar planets in terms of composition and size, but Earth is a lush blue marble. Venus, on the other hand, is a barren wasteland with a crushing atmospheric pressure and clouds of sulfuric acid. However, both planets have an ionosphere at the edge of space. This field of charged particles naturally emits radio waves, and that’s what Parker detected.
This new data allowed the team to calculate the density of Venus’ atmosphere, which is impossible to do without direct measurements. The last time scientists had such data was in 1992 when the Pioneer Venus Orbiter reached the planet. Subsequent measurements from Earth suggested that the upper atmosphere of Venus underwent significant changes during periods of solar minimum, which we just entered a few months before the flyby. Parker confirms that the planet’s ionosphere gets considerably thinner as the sun becomes less active.
Much of NASA’s work on Venus has focused on why it’s so different from Earth today. Scientists believe it was once much more Earth-like, and data like the atmospheric readings from Parker could help us understand how it morphed into the nightmarish hellscape it is today. Parker will complete four more flybys of Venus to decrease its distance from the sun on its next pass. It’s possible we’ll get even more useful data from Venus, courtesy of this solar explorer.