Water Suspected Beneath Mars

The surface features of Mars -- crossed by river deltas and sedimentary deposits -- indicate a watery past. Where that water went after the planet lost its atmosphere 3 - 4 billion years ago is an open question. But a new study suggests that quite a bit of that water moved underground rather than escaping to space. (Image credit: NASA/JPL-Caltech; research credit: V. Wright et al.; via Physics World) Read the full article

Reimagining Mars' Interior

Older models of Mars assumed a liquid metal core beneath a solid mantle of silicates, but recent studies indicate that structure is missing at least one layer. Using data from the InSight lander's seismometer, two teams independently calculated that a liquid silicate layer must surround the planet's core.  (Image credit: Mars - NASA/JPL-Caltech/University of Arizona, illustration - J. Sieben/J. Keisling; research credit: H. Samuel et al. and A. Khan et al.; via Physics Today) Read the full article

Rocking From The Waves

Not all seismic activity stems from earthquakes. In fact, much of Earth's measured seismic waves come from interactions of the ocean and atmosphere with solid ground. (Image credit: I. Mingazova; via Physics Today) Read the full article

Understanding Stars' Seismology

Our understanding of Earth's interior is based mostly on observations of seismic waves, which travel differently through our rocky crust and the molten core. Scientists similarly use seismic waves in stars to determine their interiors. (Image credit: NASA/ESA/C. O’Dell/D. Thompson, Lawrence Livermore National Laboratory; via Physics Today) Read the full article