16:00 〜 16:15
[PPS04-03] Infrasound investigations of Venus’ Interior from Balloons and from Orbit
キーワード：Venus, Infrasound, Seismology, balloon, airglow, mission
The high Venus surface temperature presents enormous challenges for conventional ways of investigating the planet’s interior with surface seismometers such as those deployed on the Moon and Mars and planned for Saturn’s moon Titan. However, the dense atmosphere readily enables detections of seismic events, as infrasound observed from balloons in the atmosphere or as electromagnetic signatures, generated by interaction of infrasound with the upper atmosphere, that can be measured by spacecraft in orbit. Since 2014 our JPL team and its partners has been working to advance the science and technology of infrasound seismology, initially using the Earth as a testbed, but now planning missions to Venus that would carry out these investigations.
Beginning with artificial sources—a seismic hammer and chemical explosions—the feasibility of detecting infrasound from balloons was demonstrated, and the low background noise achievable with a platform that moved with the wind was confirmed. Balloon flights in the troposphere and the stratosphere then characterized the signatures of natural phenomena such as the ocean microbarom and thunderstorms. In July 2019, the first balloon detection of an earthquake was accomplished. A 4.2 Mw aftershock of the Ridgecrest, California 7.1 Mw earthquake was detected with a single microbarometer sensor on a single balloon and validated with simultaneous measurements made at nearby ground seismometers. Two years later, in another opportunistic investigation, this time with balloons in the French Strateole network, infrasound signatures of two large quakes in Northern Peru (Mw = 7.5) and the Flores Sea (Mw = 7.3), as well as the massive Tonga volcanic eruption of February 2022, were recognized. The feasibility of using balloon seismic data alone to determine quake location and magnitude, as well as characterizing lithospheric properties, was thus demonstrated.
Most recently, a campaign under NASA’s Planetary Science and Technology through Analog Research (PSTAR) program targeted at a region of fracking in the U.S. led to the detection of a Mw = 2.7 quake in the Permian basin of Texas by two sensors on each of two balloons. This detection was also the first of epicentral infrasound, an atmospheric disturbance generated directly above the epicenter and propagating directly to the balloon.
These results have spurred interest in developing (a) Venus mission(s) equipped with balloons to first characterize seismic activity on Venus and subsequently locate events with a balloon network. Concepts for orbiters making complementary observations from Venus orbit of the infrared airglow signatures produced by large quakes—in excess of Mw = 5.4—have also been developed and could be implemented by small and comparatively low-cost missions. Airglow instrument-equipped orbiters have the potential for global observations and localizing the event from a single orbital vantage point.
In tandem with these Earth analog and mission design efforts, we are undertaking investigations of the number and types of seismic and volcanic signatures that we might expect on Venus, as well as modeling of both the infrasound signature at balloon altitudes and the EM signature observed from orbit. Those investigations rely on legacy radar data from Magellan and other spacecraft obtained late in the last century but are now energized with the prospect of new radar data from missions currently under development.
We will describe recent results, including progress on a vector infrasound detector or aeroseismometer. This detector has the potential for not only establishing the direction of an event from a single station but also the ability to reduce background noise from turbulence and atmospheric perturbations.
Acknowledgments: The research described in this abstract was funded by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Beginning with artificial sources—a seismic hammer and chemical explosions—the feasibility of detecting infrasound from balloons was demonstrated, and the low background noise achievable with a platform that moved with the wind was confirmed. Balloon flights in the troposphere and the stratosphere then characterized the signatures of natural phenomena such as the ocean microbarom and thunderstorms. In July 2019, the first balloon detection of an earthquake was accomplished. A 4.2 Mw aftershock of the Ridgecrest, California 7.1 Mw earthquake was detected with a single microbarometer sensor on a single balloon and validated with simultaneous measurements made at nearby ground seismometers. Two years later, in another opportunistic investigation, this time with balloons in the French Strateole network, infrasound signatures of two large quakes in Northern Peru (Mw = 7.5) and the Flores Sea (Mw = 7.3), as well as the massive Tonga volcanic eruption of February 2022, were recognized. The feasibility of using balloon seismic data alone to determine quake location and magnitude, as well as characterizing lithospheric properties, was thus demonstrated.
Most recently, a campaign under NASA’s Planetary Science and Technology through Analog Research (PSTAR) program targeted at a region of fracking in the U.S. led to the detection of a Mw = 2.7 quake in the Permian basin of Texas by two sensors on each of two balloons. This detection was also the first of epicentral infrasound, an atmospheric disturbance generated directly above the epicenter and propagating directly to the balloon.
These results have spurred interest in developing (a) Venus mission(s) equipped with balloons to first characterize seismic activity on Venus and subsequently locate events with a balloon network. Concepts for orbiters making complementary observations from Venus orbit of the infrared airglow signatures produced by large quakes—in excess of Mw = 5.4—have also been developed and could be implemented by small and comparatively low-cost missions. Airglow instrument-equipped orbiters have the potential for global observations and localizing the event from a single orbital vantage point.
In tandem with these Earth analog and mission design efforts, we are undertaking investigations of the number and types of seismic and volcanic signatures that we might expect on Venus, as well as modeling of both the infrasound signature at balloon altitudes and the EM signature observed from orbit. Those investigations rely on legacy radar data from Magellan and other spacecraft obtained late in the last century but are now energized with the prospect of new radar data from missions currently under development.
We will describe recent results, including progress on a vector infrasound detector or aeroseismometer. This detector has the potential for not only establishing the direction of an event from a single station but also the ability to reduce background noise from turbulence and atmospheric perturbations.
Acknowledgments: The research described in this abstract was funded by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.