Level 1 — Absolute Beginner

Mars is the fourth planet from the Sun. It is about half the size of Earth. Scientists study Mars because they want to learn about its rocks and its inside.

Scientists found something new about Mars. They learned that the inside of Mars is not the same in the north and in the south. The south side is much hotter than the north side.

A scientist named Alexander Berne led this study. He used a special method. The method looks at how Mars bends a little bit when the Sun and other planets pull on it with gravity. This method is called tidal tomography.

The hot rock under the south of Mars may still be a little bit melted. This is a big discovery. It helps explain some old mysteries about Mars.

planet

A large round object in space that moves around a star, like Mars or Earth.

inside

The part of something that is not on the outside; the middle or deep part.

hotter

Having more heat than something else.

scientist

A person who studies the world to learn new facts.

gravity

The force that pulls objects toward each other, like the pull that keeps us on the ground.

method

A way of doing something, often used to find something out.

melted

Changed from solid to soft or liquid because of heat.

mystery

Something that is strange and not fully understood yet.

Level 2 — Elementary

For a long time, scientists thought that the inside of Mars was shaped in a similar way on both the north side and the south side. A new study, published in the journal Nature on August 27, 2026, shows that this idea was wrong.

The study was led by Alexander Berne, who finished his PhD at Caltech in 2026 and now works at the University of Arizona. His team used a technique called tidal tomography. This technique studies how a planet's shape flexes slightly when gravity pulls on it, and this helps scientists map what is happening deep inside the planet.

The team discovered that the mantle, the thick layer of rock under the surface, is much hotter beneath the southern highlands of Mars than beneath the northern half of the planet. The difference is about 200 to 400 degrees Celsius. Some of this hot rock in the south may even be partly molten, meaning partly melted.

This discovery helps explain two old mysteries about Mars: strange patches of magnetism found in rocks in the south, and unusual behavior of marsquake waves recorded by NASA's InSight lander, which worked on Mars from 2018 until 2022. Scientists still do not fully know why this hot and cold divide exists.

technique

A particular way of doing a task, especially one that needs skill.

flex

To bend slightly, often because of pressure or force.

mantle

The thick layer of rock inside a planet, found under the outer surface.

highlands

An area of land that is higher than the land around it.

molten

Melted by heat, especially describing rock or metal that has turned soft or liquid.

magnetism

A force in certain materials that can attract or push away other materials.

seismic

Related to shaking or waves caused by movement inside a planet, such as an earthquake or marsquake.

divide

A clear difference or separation between two things.

Level 3 — Intermediate

Planetary scientists have long assumed that the interior of Mars is broadly symmetrical, with the mantle beneath the northern lowlands behaving much like the mantle beneath the southern highlands. A study published in the journal Nature on August 27, 2026 challenges that assumption directly, revealing a hidden thermal divide running through the planet's interior.

The research was led by Alexander Berne, who completed his PhD at Caltech in 2026 and is now a postdoctoral associate at the University of Arizona. Rather than relying only on seismic data, the team applied a technique known as tidal tomography, which analyzes the subtle way a planet's shape flexes as it is pulled by gravity, in order to infer conditions deep beneath the surface.

According to the findings, the mantle beneath Mars's southern highlands runs roughly 200 to 400 degrees Celsius hotter than the mantle beneath the northern hemisphere, and portions of it may still be partially molten. Because the origin of this divide is not yet fully explained, researchers are left with a genuine open question about how such a striking imbalance could persist for so long inside a planet once thought to have cooled fairly evenly.

The discovery offers a compelling explanation for two puzzles that have troubled Mars researchers for years: isolated patches of unusually strong magnetism in southern rocks, and the surprising way seismic waves recorded by NASA's InSight lander, active on Mars from 2018 until its retirement in 2022, lost energy far more quickly when traveling through the southern interior than through the northern one. A warmer, once more active mantle in the south may have driven greater volcanic and magnetic activity there in the planet's ancient past, leaving iron bearing minerals with a lasting magnetic signature.

symmetrical

Having matching parts on each side; balanced in shape or structure.

interior

The inside part of something, especially a large object like a planet.

postdoctoral

Describing research work done after completing a PhD degree.

infer

To work out or conclude something based on evidence rather than direct observation.

imbalance

A lack of equality or balance between two things.

persist

To continue to exist over a long period of time.

retirement

The point at which something, such as a spacecraft, stops being actively used.

signature

A distinctive pattern or mark that shows evidence of something.

Level 4 — Advanced

For decades, planetary scientists modeled the Martian interior as broadly hemispherically uniform, an assumption that, while convenient, always sat somewhat uneasily alongside the planet's well known surface dichotomy, the stark contrast between the low lying northern plains and the ancient, cratered southern highlands. A study published in the journal Nature on August 27, 2026 now demonstrates that this assumption does not hold beneath the surface either, uncovering a substantial and previously hidden thermal divide within Mars's mantle.

Led by Alexander Berne, a Caltech PhD graduate from the class of 2026 now serving as a postdoctoral associate at the University of Arizona, the research team turned to a comparatively novel approach called tidal tomography. Rather than depending solely on the sparse seismic record gathered by a single lander, the method infers deep interior structure from the subtle way a planet's shape deforms under the periodic gravitational tug it experiences, offering a complementary window into regions that direct seismic imaging alone could not fully resolve.

The results are striking: the mantle beneath the southern highlands appears to run roughly 200 to 400 degrees Celsius hotter than its northern counterpart, and portions of that southern mantle may remain partially molten to this day. Crucially, the researchers are candid that the underlying cause of this asymmetry has not yet been pinned down, leaving open a substantive question for future work about what dynamic process could sustain such a pronounced thermal contrast over geological time.

What the finding does resolve, convincingly, is a pair of long standing puzzles. First, the localized patches of anomalously strong magnetism detected in iron bearing minerals across the southern crust now find a plausible mechanism: a hotter, once more vigorously convecting mantle likely sustained greater volcanic and magnetic activity in the region's deeper past. Second, and perhaps more tellingly, the finding accounts for an oddity long noted in data from NASA's InSight lander, which operated on Mars from 2018 until its retirement in 2022, whose seismic waves consistently attenuated, that is, lost energy, far more rapidly when propagating through the southern interior than when crossing the north. Taken together, the results reframe Mars not as a planet with a broadly settled, symmetrical interior, but as one still carrying the asymmetric thermal fingerprint of its early history.

dichotomy

A division or contrast between two things that are very different from each other.

hemispherically

In a way that relates to one half of a sphere, such as the northern or southern half of a planet.

deform

To change shape, especially under pressure or force.

resolve

To clearly detect or distinguish detail, or to settle a question with a clear answer.

asymmetry