[ad_1]
“Trying to detect naturally occurring earthquakes from balloons is challenging, and when you look at the data for the first time, you can be disappointed, because most low-magnitude earthquakes don’t produce strong sound waves in the atmosphere,” said Quentin Presaud, a seismologist at the Lab. Seismology at Caltech and the Norwegian Seismic Array (NORSAR) in Oslo, Norway. “All kinds of environmental noises are detected; even the balloons themselves generate noise.”
During previous tests, researchers detected sound signals from seismic waves generated by a seismic hammer (a heavy mass that is dropped to the ground), as well as explosives that exploded on the ground beneath tethered balloons. But could researchers do the same with free-floating balloons on top of a natural earthquake? The main challenge among others: There was no guarantee of an earthquake even when the balloons were high.
On July 22, they had a lucky chance: Earth-based seismometers recorded a magnitude of 4.2 aftershocks about 50 miles (80 kilometers) away. About 32 seconds later, one of the balloon detected low-frequency acoustic vibration — a type of sound wave below the human hearing threshold called ultrasound — washing it as it climbed to an altitude of about 3 miles (4.8 kilometers). Through analysis and comparisons with computer models and simulations, the researchers confirmed that they had detected, for the first time, a naturally occurring earthquake from a balloon-borne instrument.
“Because there is a dense network of seismograph ground stations in Southern California, we were able to get the ‘ground truth’ regarding the earthquake’s timing and location,” said Presaud, the study’s lead author. “The wave we detected was closely related to nearby ground stations, and when compared to the model data, we were convinced – we heard an earthquake.”
Researchers will continue to fly balloons over seismically active regions to become more familiar with the infrasound signatures associated with these events. By adding several scales to the same balloon and flying several balloons simultaneously, they hope to determine where the earthquake occurred without the need for confirmation from ground stations.
From California to Venus
It has already been proven that sending balloons to Venus is possible. Two Vega mission balloons were deployed there in 1985 by a Soviet-led cooperative that relayed data for more than 46 hours. Neither of them carried instruments to detect seismic activity. This study now shows that an ultrasound detection technology on Venus may also be possible. In fact, because Venus’s atmosphere is denser than Earth’s, sound waves travel more efficiently.
“The acoustic coupling of atmospheric earthquakes has been calculated to be 60 times stronger on Venus than on Earth, which means that earthquakes are easier to detect from cold layers of Venus’s atmosphere between 50 to 60 kilometers away. [about 31 to 37 miles] up,” said JPL technologist Siddharth Krishnamurthy, principal investigator for the analysis effort. “We should be able to detect earthquakes, volcanic processes, and outgassing events while determining activity levels.”
What Krishnamurth is most interested in about balloons flying on Venus is that scientists can use them to drift over areas that appear to be seismically active based on satellite observations and see if they really are. “If we drift over a hotspot, or what looks like a volcano from orbit, the balloon will be able to listen for acoustic clues to see if it’s really behaving like a land-based volcano,” said Krishnamurthy, who was also the company’s technical lead. Ridgecrest Balloon Campaign. “This way, the balloons can provide ground truth for satellite measurements.”
As the Balloon Venus team continues to explore these possibilities, NASA colleagues will press ahead with two recently selected missions to go to Venus between 2028 and 2030: VERITAS will study the planet’s surface and interior, and DAVINCI+ will study its atmosphere. The European Space Agency (ESA) has also announced its own mission to Venus, EnVision. These missions will provide new clues as to why the formerly Earth-like planet has become inhospitable.
[ad_2]
Picture Credit!