Level 1 — Absolute Beginner
Scientists find a warm place deep inside Mars. It is in the southern half of the planet. It is under the ground, far down in a layer called the mantle.
The warm place is 200 to 400 degrees Celsius hotter than the rest of the mantle. That is a big difference.
How do scientists see inside a planet? They watch how Mars changes shape. The Sun pulls on Mars a little, like the Moon pulls on the sea on Earth. Mars moves in an oval path, so the pull changes. The planet stretches and squeezes.
A team at the University of Arizona wrote about it in a big science journal called Nature.
- planet
- A very large round object that moves around a star.
- mantle
- The thick hot layer inside a planet, under the top crust.
- degrees
- Units used to measure heat.
- layer
- One level of something.
- squeeze
- To press something from the sides.
- oval
- A shape like an egg.
- journal
- A magazine where scientists share their work.
- team
- A group of people who work together.
Level 2 — Elementary
Scientists have found a huge warm area deep inside Mars. It lies under the southern highlands and is about 200 to 400 degrees Celsius hotter than the mantle around it. The discovery was published in the journal Nature.
The team, led by Alexander Byrne at the University of Arizona, used a method called tidal tomography. Mars does not move around the Sun in a perfect circle. Because its distance from the Sun changes, the Sun's gravity stretches and squeezes the planet by different amounts.
The size of this tiny change depends on how stiff the inside of Mars is. The team found that the mantle is not the same everywhere. In some places it is more than 20 percent different in stiffness, and the pattern runs from north to south.
The warm area sits under the same line that divides Mars into low northern plains and high southern highlands. Scientists think the heat could come from moving hot rock, or from the thick southern crust, which acts like a warm blanket.
- tidal tomography
- A way to look inside a planet by studying how gravity changes its shape.
- highlands
- High land, such as hills and mountains.
- gravity
- The force that pulls objects toward each other.
- stiff
- Hard to bend or stretch.
- crust
- The thin outside layer of a planet.
- anomaly
- Something that is different from what is normal.
- plains
- Large flat areas of land.
- blanket
- A cover that keeps something warm.
Level 3 — Intermediate
Researchers have found evidence of a thermal anomaly roughly 200 to 400 degrees Celsius warmer than its surroundings in the mantle beneath the southern highlands of Mars, according to a study in Nature led by Alexander Byrne of the University of Arizona. The work is the first to apply a technique called tidal tomography to map large scale differences inside the Martian mantle.
The method rests on a simple idea. Because Mars follows an elliptical orbit, the Sun's gravity deforms the planet by different amounts over the Martian year, raising a tidal bulge that rises and falls. Spacecraft orbiting Mars can measure that bulge precisely, and how large it is depends on the stiffness of the interior.
The measurements did not fit a mantle that was the same everywhere. They are best explained if the effective shear modulus, a measure of stiffness, varies by more than 20 percent in a roughly north to south pattern that matches the crustal dichotomy, the sharp divide between Mars's low northern lowlands and its elevated southern highlands.
The authors suggest two explanations. The heat could be a sign of regional mantle convection, or it could be insulation: a thick southern crust acting like a lid that has trapped warmth for billions of years. Either way, the result hints that the planet's early structure may still shape its deep interior today.
- thermal anomaly
- A region whose temperature is unusual compared with its surroundings.
- elliptical
- Shaped like a stretched circle.
- tidal bulge
- A raised area on a planet or moon caused by gravity from another body.
- shear modulus
- A measure of how stiff a material is when it is pushed sideways.
- crustal dichotomy
- The sharp divide between Mars's northern lowlands and southern highlands.
- convection
- The movement of heated material that rises while cooler material sinks.
- insulation
- A material or layer that keeps heat from escaping.
- hints
- Suggests without saying directly.
Level 4 — Advanced
A study in Nature reports a thermal anomaly of 200 to 400 degrees Celsius preserved in the present day mantle beneath the southern highlands of Mars, a finding led by Alexander Byrne of the University of Arizona that offers a rare glimpse into the deep interior of a planet whose interior is still poorly mapped, even after seismometer readings. It is the first application of tidal tomography to resolve large scale variations in the Martian mantle.
The technique exploits the eccentricity of the planet's orbit. As Mars swings nearer to and farther from the Sun, solar gravity flexes the planet by a varying amount, producing a tidal bulge whose amplitude and timing, tracked by orbiting spacecraft, betray the stiffness of the material within.
Observed deviations proved irreconcilable with a laterally uniform mantle. They are explained instead if the effective shear modulus varies by more than 20 percent in a broadly north to south pattern that closely tracks the surface expression of the crustal dichotomy, the stark contrast between the subdued northern lowlands and the heavily cratered southern highlands.
The authors propose that the anomaly reflects either regional mantle convection or thermal insulation by a thick southern crust that has persisted for billions of years. Both scenarios imply that the asymmetry which shaped Mars's earliest geography still leaves a thermal fingerprint, a notion that could refine models of how the planet cooled and why it lost its once active volcanic engine.
- seismometer
- An instrument that measures vibrations inside a planet.
- eccentricity
- How far an orbit departs from a perfect circle.
- amplitude
- The size of a wave or swing from its middle point.
- betray
- To reveal something that was meant to stay hidden.
- irreconcilable
- Impossible to bring into agreement.
- laterally
- From side to side across a surface.
- asymmetry
- A lack of equal balance between two sides.
- refine
- To improve something by making small changes.
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