An opportunity in 2019 lays the groundwork for balloon-based detectors on Venus working to solve a key puzzle.
The sky of Venus could become a busy place in the next decade, utilizing technologies that have been field tested here on Earth.
A team from NASA JPL-Caltech hypothesized that terrestrial earthquakes should also generate low-frequency infrasound sound waves that would be transmitted through the atmosphere as changes in air pressure from the ground. Although these sound waves are difficult to detect, they should be measured with highly sensitive barometers in the air.
One of the balloons from the study in the field. NASA / JPL-Caltech
The team had the opportunity to put this idea to the test in 2019. In early July, a series of powerful earthquakes struck the city of Ridgecrest, California. Over 10,000 aftershocks followed in the next six weeks. This gave the team the opportunity to fly instruments on board four heliotrope balloons, which rise to around 18 to 24 kilometers in the warmth of the daytime sun and return to earth at night.
Previous experiments detected deliberately man-made earthquakes caused by seismic hammers or explosives, but analyzing weak low-frequency waves is orders of magnitude more difficult. Environmental noise – including the vibrations of the balloons themselves – had to be taken into account.
The team paused on July 22 when it detected a 4.2 magnitude aftershock. Multiple readings from separate balloons indicated the event, which was verified by ground sensors. The results were published in the June 2021 issue of Geophysical Research: Letters.
The enigma of Venus geology
But the NASA JPL team has higher ambitions, such as floating balloon-assisted barometric sensors in Venus’ atmosphere to solve a key puzzle: Was the planet active in the past and is it active today?
“Much of our understanding of the Earth’s interior – how it cools and its relationship to the surface, where life resides – comes from analyzing seismic waves that traverse regions as deep as the Earth’s inner core,” says Jennifer Jackson (Caltech Seismological Laboratory) in a recent press release. “Tens of thousands of ground-based seismometers populate spatially dense or permanent networks and enable this possibility on earth. We do not have this luxury on other planetary bodies … The extreme environment of Venus requires that we investigate new detection techniques. “
An artist’s idea of a balloon flying in the sky of Venus. Photo credit: NASA / JPL-Caltech
Detecting tremors with a balloon … on Venus
The idea is to measure changes in air pressure in height to detect tremors below. The good news is, while conditions are hellish on Venus’ surface, things are much milder in the planet’s upper atmosphere. While a lander on Venus will succumb to the high temperatures and enormous pressure on the surface of the planet after just a few hours, a balloon-based platform could be operated for weeks or even months. A network of balloon-style barometric stations could go a long way toward understanding the enigmatic Venusian interior.
A Venus balloon prototype in the laboratory on Earth. Photo credit: NASA / JPL-Caltech
Venus Exploration: Past, Present and Future
The Soviet Union paved the way for the exploration of Venus with the successful lands of the Venera series. The Soviets also conducted the first successful Vega 1 and 2 interplanetary balloon missions in 1986.
A scale model of a Vega comet flyby mission with a decent Venus package at the Udvar Hazy center on Earth. Public domain.
Although NASA has not been to Venus since the end of the Magellan Orbiter mission in 1994, the agency plans to send the VERITAS and DAVINCI + missions to Venus in the next decade. More exotic ideas include things like a steampunk-style wind-up rover powered by the wind.
It will be fascinating to see balloon missions in the sky of Venus one day. But for now, terrestrial balloon missions here on earth will pave the way for space-based technology.