Launched in 2018 with the mission of studying the Sun very close, the Parker Solar Probe probe approached Venus to perform a maneuver known as “gravitational thrust”. In order to reach the Sun, the spacecraft must use the impulse of a planet like Venus to change its orbit, reducing its perihelion in each of the passages around the sun, until reaching the maximum approach. Parker made the third overflight there in July 2020 and surprised the scientists with a radio noise.
Although the signal was natural, the researchers were not exactly waiting for it. Glyn Collison, of the Goddard Space Flight Center of NASA he says that when the Solar Parker FIELDS instrument detected a low frequency signal for seven minutes, it was unable to identify it immediately. However, the abrupt change in data frequency caught Collinson’s attention because, somehow, the signal was familiar to him. “So, the next day, I woke up,” he said, “and I thought, ‘My God, I know what this is!’”
Collinson recognized the signal because he had worked extensively with atmospheric data from Venus before – enough to be recognized as an expert on the planet. He has already analyzed all Venus data from previous missions, such as NASA’s Pioneer Venus Orbiter and ESA’s Venus Express (European Space Agency). Several times. Then, when faced with the frequency captured by Solar Probe, he realized that the probe had traversed the upper Venusian atmosphere. A good surprise that will allow us to study the effects of solar activities on the climate of Venus.
In terms of size and structure, Venus is not so different from Earth, and some researchers have thought that it was once a favorable place for liquid water in the past. However, our neighbor today is known as the “infernal planet”, and the reason is easy to imagine – Venus is hot and toxic, not only for the forms of life we know, but also for our scientific instruments. None of the probes sent to Venus to this day survived for more than a few minutes.
Fortunately, it is not necessary to be on Venus to know a little about its atmosphere. When passing by, the Parker Parker probe collected a lot of useful information, mainly about the thickness of the upper atmosphere. This was the first direct measurement of the Venusian atmosphere in almost 30 years, and the data can now be used to compare with older ones. Has Venus changed? Well, the signals picked up look quite different now, and a study confirmed that the planet’s upper atmosphere is undergoing changes over the current solar cycle.
The solar cycle refers to the activity of the Sun and corresponds to 11 years. During this time, our star reaches the so-called solar minimum, advances to the solar maximum, and then returns to the lowest activity. For us, it is essential to understand the effects of the solar maximum in the Earth’s atmosphere and in the entire Solar System, which, of course, includes Venus. However, without direct observation, it would not be possible to discover much, and this is where the radio signal becomes important.
The last time direct measurements of Venus’ ionosphere were obtained was in 1992, when the Sun was close to the solar maximum. In the years that followed, while the Sun was going to the minimum, terrestrial telescopes suggested that changes in the ionosphere occurred – it became that it is at the top, which facilitates the escape of gases into space. But that needed to be confirmed, and it was through the Solar Parker flight and the “accidental” collection of ionosphere signals on Venus that researchers were able to have more confidence in this hypothesis. In fact, they concluded that Venus’ ionosphere is much thinner compared to previous measurements made during the solar peak.
This new understanding will help researchers better understand what happened to the Venus climate. But for that, they will have to find out why the Venusian ionosphere is thinning during the solar minimum, and this is particularly interesting because, if Venus was already so similar to Earth, we want to avoid what may have happened there so that the planet can become make it so unusual. If it is true that the Venus ionosphere is subject to leaks of energized gases into space during the solar minimum, the next step should be to collect data on the changes that will take place there in the next phases of the solar cycle.
Source: NASA
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