Since about three years ago, NASA's Parker Solar Probe has been using Venus's gravity to fly by the sun, collecting data. But on its most recent flyby mission, Parker came as close as ever to our interstellar neighbor Venus (just 833 kilometers above the surface) and picked up some unexpected natural radio signals that weren't coming from aliens
Parker picked up low-frequency radio signals for up to seven minutes during its closest approach to Venus, the report said. NASA studied the cause of the radio waves and realized that the Parker probe must have passed through Venus's upper atmosphere, known as the ionosphere -- a feat that scientists hadn't planned for, but was nonetheless exhilarating. The frequency recorded by the detector matches the signal type of the surrounding gas. This is the first direct observation of the Venusian atmosphere in nearly 30 years.
The scientists then used these signals to calculate the density of the ionosphere and compared them with past measurements and estimates. The measurements came shortly after the sun entered its minimum, the least active phase of its 11-year cycle.
NASA scientists have found that the atmosphere of Venus is now thinner than it was during the last solar maximum, when direct observations were made. Other observations and hypotheses have suggested the trend, but this is the first time scientists have confirmed it through direct observation. The findings are published in the American journal Geophysical Letters.
"I am very excited to have new data on Venus," NASA Venus expert Glenn Collison said in a statement. He likened the discovery to a free ride and said Venusian experts were eager to put the chance find to good use, even though Parker's main mission was to observe the sun.
Noor Rawafi, Parker Solar Probe project scientist, said in the same statement that while the team is targeting the sun, "we will not miss the opportunity to gather scientific data and gain insight into mysterious planets like Venus."
The chance observation was a spectacular glimpse. Venus is often called Earth's twin, but its atmosphere and environment are very different. Venus lacks a magnetic field and its surface temperature is completely uninhabitable. But the new findings suggest that Venus' atmosphere can change under the influence of the sun. Further research may build on this finding, hoping to understand why Venus became so different from Earth.
Parker will continue its mission for the next four years. During that time, NASA hopes Parker will reach the outermost layer of the sun's atmosphere, passing through the corona and reducing its approach to about one-seventh the closest any spacecraft has ever gotten to the sun.