Mars could help us find water on the red planet

Earth is a seismically active planet, and scientists have discovered how to use seismic waves from earthquakes to study its interior. We use artificially generated seismic waves to identify underground petroleum-bearing formations. When the InSIGHT (Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport) lander was sent to Mars, it sensed Mars to learn more about the planet’s interior.

Researchers think they can use marsquaks to answer one of Mars’ most important questions: Does the planet have water trapped in its bottom?

Ground-penetrating radar can tell what’s underground on Earth. However, it has limitations. It reaches about 30 meters underground in low conductivity materials and about one meter in conductive materials. Scientists are developing other methods including Seismic Interferometers, to use seismic science to detect deep water bodies, but those methods are not fully developed. Because there is a lot of water inside the Earth it creates noisy signals.

These methods are not applicable to Mars, where equipment is limited.

However, researchers from Penn State University think they could use different types of seismic waves to detect surface water on Mars. This is called the seismic electricity method, and it combines seismology and electromagnetism. It senses electromagnetic signals from the propagation of seismic waves in a planet’s interior.

Their new research, “Characterizing liquid water in deep Martian reservoirs: a seismic-electrical approachPublished in JGR Planets. Nolan Roth, a PhD candidate in the Department of Geosciences at Penn State, is the lead author.

„The scientific community has theorized that there were oceans on Mars and that during its history, all that water was gone,” Roth said. “But there is evidence that water is trapped somewhere underground. We couldn’t find it. The idea is that if we can detect these electromagnetic signals, we will find water on Mars.

Seismology works by detecting elastic waves propagating through the Earth. These waves are divided into subtypes, specifically B-waves or primary waves and S-waves or secondary waves. Each type of wave travels differently depending on the material it moves through. Broadly speaking, B-waves travel faster than S-waves, so they reach seismic sensors at different times. Differences in time and other factors reveal the properties and density of the material through which the waves travel.

Seismic electrical method detects electromagnetic signals produced by seismic waves rather than waves. As waves travel through a planet, material such as rock or water moves differently in response. Those differences create magnetic fields that surface sensors can detect.

„If we listen to marsupials moving on the surface, if they’re going through water, they’re generating these amazing, unique signals of electromagnetic fields,” Roth said. „These signals detect current, modern-day water on Mars.”

This method is best suited for Mars. On Earth, detection is difficult because water is mixed not only in aquifers but also underground. But Mars is very dry, except for possible subterranean aquifers. If we detect buried water on Mars with seismic electricity, it is almost certainly an underground aquifer.

„In contrast to how seismic signals often appear on Earth, the Martian surface naturally removes noise and exposes useful data that allows us to characterize many hydrological properties,” said Deuan Zhu, associate professor of geosciences at Penn State and Roth’s advisor. .

The seismic electric mode includes two types of electromagnetic fields: parallel seismic waves and interface responses (IR). There are two types of interface responses: radiative interface responses (RIRs) and evanescent interface responses (EIRs.)

„Interfacial responses (IRs) are generated when a seismic wave creates a charge imbalance at a saturated interface,” the authors explain. Regardless of how much liquid is in the medium, RIRs radiate independently of the electromagnetic velocity from the interface. EIRs are generated when a seismic wave strikes a saturated interface at a certain angle. Both types of IR are generated in the presence of mobile fluids, but do not require a saturated layer for further propagation. RIRs, in particular, can travel through kilometers of reef. Both types of interface responses can be separated and analyzed separately.

All of this adds up to a new method of „seeing” inside Mars and finding saturated layers.

Roth and his co-researchers began by building a model of Mars. Then, they added water bodies to simulate how a seismic electricity system would work. The results show that seismic technology can be used to determine details about aquifers, including their dimensions and chemical properties such as salinity.

„Aquifer depth, thickness, and size affect interface response arrival times and shape,” the authors write in their research. „Aquifer water saturation fraction, chemistry, and salinity strongly affect interface response strength but have no effect on waveform shape.”

„Seismo-electric signals can be used to constrain the estimation of aquifer depth, size, location and total chemical composition,” they added.

„SE measurements provide a way to detect and image Martian groundwater kilometers below the surface,” the authors write in their conclusion. „As SE exploration becomes more widespread on Earth, this study represents the method’s first forays to other worlds.”

„If we can understand the signals, we can go back and characterize the water bodies themselves,” Roth said in a press release. „This will give us more hurdles than ever to understand water on Mars today and how it has changed over the last 4 billion years. And it will be a big step forward.”

The most exciting part about using a seismic power system on Mars is that it doesn’t require a new mission. NASA’s Inside Lander acquired a large amount of seismic data during its mission. It had a magnetometer, and future work will combine signals from both Opens a New Window.

If this method proves successful, seismometers and magnetometers could be added to future missions not only to Mars but also to other worlds. Frozen ocean moons like Europa and Enceladus are prime study targets in the search for life, and the technique could work there.

„It shouldn’t be limited to Mars — it’s capable of measuring the thickness of icy oceans on Jupiter’s moons, for example,” Zhu said. „The message we want to convey to the community is that these promising physical phenomena – which have received little attention in the past – may have great potential for planetary geophysics.”