The 15 January 2022 climactic eruption of Hunga volcano, Tonga, produced an explosion in the atmosphere of a size that has not been documented in the modern geophysical record. The event generated a broad range of atmospheric waves observed globally by various ground-based and spaceborne instrumentation networks. Most prominent was the surface-guided Lamb wave (≲0.01 hertz), which we observed propagating for four (plus three antipodal) passages around Earth over 6 days. As measured by the Lamb wave amplitudes, the climactic Hunga explosion was comparable in size to that of the 1883 Krakatau eruption. The Hunga eruption produced remarkable globally detected infrasound (0.01 to 20 hertz), long-range (~10,000 kilometers) audible sound, and ionospheric perturbations. Seismometers worldwide recorded pure seismic and air-to-ground coupled waves. Air-to-sea coupling likely contributed to fast-arriving tsunamis. Here, we highlight exceptional observations of the atmospheric waves.

Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.

It has previously been suggested that ionospheric perturbations triggered by large dip‐slip earthquakes might offer additional source parameter information compared to the information gathered from land observations. Based on 3D modeling of GPS‐ and GLONASS‐derived total electron content signals recorded during the 2011 Van earthquake (thrust, intra‐plate event, M_w = 7.1, Turkey), we confirm that coseismic ionospheric signals do contain important information about the earthquake source, namely its slip mode. Moreover, we show that part of the ionospheric signal (initial polarity and amplitude distribution) is not related to the earthquake source, but is instead controlled by the geomagnetic field and the geometry of the Global Navigation Satellite System satellites constellation. Ignoring these non‐tectonic effects would lead to an incorrect description of the earthquake source. Thus, our work emphasizes the added caution that should be used when analyzing ionospheric signals for earthquake source studies.

The amplitude asymmetry and initial polarity of seismic induced ionospheric perturbations around the epicenter are considered to be important in providing information about the rupture propagation and related vertical surface deformation. To comprehend this, we study ionospheric perturbations related to the 12 May 2015, M_w 7.3 Nepal earthquake. We model the coseismic slip associated with the event using the interferometric synthetic aperture radar derived surface deformation data. The ionospheric perturbations associated with the obtained surface deformation are explained in terms of rupture propagation, favorable geomagnetic field‐wave coupling, and satellite geometry effects. We discuss the effects of phase cancelation on the perturbation evolution for various receiver satellite line‐of‐sight configurations invoking an elementary version of satellite geometry factor. The present study thus elucidates further the role of nontectonic forcing mechanisms while identifying ground source pattern using the associated ionospheric perturbations.

Acoustic waves in planetary atmospheres couple into the solid surface, producing ground displacements that can be measured using seismometers. On 26 November 2018, the InSight mission successfully landed on Mars. Its objectives include studying Mars' interior using the seismometer SEIS (Seismic Experiment for Interior Structures) and the atmosphere through the weather station APSS (Auxiliary Payload Sensor Suite). Because InSight is the first mission capable of studying infrasound on Mars, we investigate the signature of infrasound both in terms of air pressure and ground velocities. Using numerical simulations, we characterize (1) the acoustic propagation pattern in Martian dusk and (2) the mechanical atmosphere‐to‐ground coupling under acoustic waves. Then, using SEIS data, we demonstrate that two low‐frequency monotone events (S0133a and S0189a) are in fact infrasound trapped in the atmospheric nocturnal surface waveguide. We base our demonstration on the following facts. (1) Seismic signals rarely produce, at a given station, a single frequency varying from one event to the other. (2) No clear seismic phases have been identified for such events. (3) The observed SEIS signals present the characteristics expected for trapped infrasound observed through their compliance effects (specific frequency response, more energy on the vertical component, ±90° phase shift between vertical and horizontal components, and no detection on pressure sensor at these low amplitude levels). Our simulations of the nocturnal waveguide's response are however subject to uncertainties because (1) it relies on the sol‐to‐sol variability of the atmosphere, and (2) subsurface properties are not properly known at this time.