When flying close to the planet Venus In July 2020, NASA’s Parker Solar Probe discovered an odd number.
When it sank 833 kilometers (517 miles) off the surface of Venusian, the instruments of the study recorded a low-frequency radio signal – an indication that Parker had slid through the ionosphere of a layer of the planet’s upper atmosphere.
This is the first time a tool has been able to record directly In situ Measurements of the upper atmosphere of Venus over nearly three decades, and recorded data give us a new understanding of how Venus changes when it responds to rotation in the sun.
“I was very excited to get new data from Venus.” Astronomer Clin Collinson said Of NASA’s Goddard Space Flight Center.
Venus is a fascinating world for us here on Earth. It is very similar to our own planet in size and composition, but very different: a toxic, annoyingly hot hell world, which is not entirely hospitable to life as we know it.
Planetary scientists and astronomers are looking for other habitable worlds in the Milky Way to see how the two planets could have evolved into such radically different animals.
Yet the work of exploring Venus is relatively limited. There is not much point in sending landers; They cannot live on the planet’s surface at 462 degrees Celsius (864 degrees Fahrenheit).
Due to the incredibly thick atmosphere of carbon dioxide and sulfuric acid rain clouds, it is difficult to tell what is happening on the surface.
For these reasons, Venus has at times not been a popular destination for dedicated missions (Japan’s Akatsuki Orbiter is the latest exception), and a lot of our latest data has come from tools with other primary purpose, such as Parker Solar. Investigation.
As Parker continues his mission to study the sun in more detail, it uses Venus for gravity-assisted maneuvers – slingshot around the planet to change speed and trajectory. It was on one of these gravity-assisted flippers that the instruments of the study recorded the radio signal.
Collinson, who has worked on other planetary missions, noted odd familiarity that he could not put in the form of a signal.
“Then the next day, I woke up.” he said. “I thought, ‘God, I know what this is!'”
This is the same signal recorded by Galileo’s study as it passed through the ionic orbits of Jupiter’s moons – a layer of the atmosphere found on Earth. Tuesday, Ionizes solar radiation atoms, resulting in the formation of charged plasma that produces low frequency radio emissions.
Once the researchers realized what the signal was, they were able to use it to calculate the density of the Venusian ionosphere and compare it to the last direct measurements taken on the way back in 1992. Attractively, the array of ionosphere sizes was thinner than it was in the new measurements in 1992.
The team believes this has something to do with solar cycles. Every 11 years, the sun’s poles change places; The south is north and the north is south. It is not clear what drives these cycles, but we do know that the poles change when the magnetic field is weak.
The Sun’s magnetic field controls its activity – i.e. solar dots (temporary areas of strong magnetic fields), solar flares and coronal mass discharges (produced by the rupture of magnetic field lines) – this stage of the cycle manifests itself as a very period of minimal activity. This is called the solar minimum.
As the poles change, the magnetic field strengthens, and the solar activity rises to the maximum of the sun before dropping back to the next pole switch.
Measurements of Venus from Earth stated that Venus’ ionosphere coincides with solar cycles, growing thicker at maximum and thinner at sunset. But without direct measurements, it was difficult to confirm.
Well, what do you think? The 1992 measurement was taken at a time close to the solar maximum; The 2020 measurement is close to the solar minimum. They are both compatible with earth-based measurements.
“When multiple trips confirm the same result, one after the other, it gives you a lot of confidence that the thinner is real.” Said astronomer Robin Ramstadt University of Colorado, Boulder.
It is not clear why the solar cycle has this effect on the ionosphere of Venus, but there are two leading theories.
First, the upper limit of the ionosphere can be compressed to a low altitude during solar exposure, which prevents ionized atoms from flowing to the night side, resulting in a thin night side ionosphere. Second, the ionosphere leaks into space at breakneck speed during the solar minimum.
None of these algorithms can be ruled out by Parker data, but the team hopes that future missions and observations can clarify what is going on. In turn, this will help us better understand why Venus exists compared to Earth.
Maybe it’s time for another Venus mission, right?
Research has been published Geophysical Research Letters.
Credit for Best Picture: Parker’s July 2020 Flying Venus. (NASA / Johns Hopkins APL / Naval Research Laboratory / Guillermo Stenburg and Brendan Gallagher)