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Study Details Differences between Deep Interiors of Mars and Earth

An undated artist’s depiction of the Martian interior and the paths taken by seismic waves as they traveled through the planet’s core. (NASA/JPL and Nicholas Schmerr/Handout via Reuters)
An undated artist’s depiction of the Martian interior and the paths taken by seismic waves as they traveled through the planet’s core. (NASA/JPL and Nicholas Schmerr/Handout via Reuters)
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Study Details Differences between Deep Interiors of Mars and Earth

An undated artist’s depiction of the Martian interior and the paths taken by seismic waves as they traveled through the planet’s core. (NASA/JPL and Nicholas Schmerr/Handout via Reuters)
An undated artist’s depiction of the Martian interior and the paths taken by seismic waves as they traveled through the planet’s core. (NASA/JPL and Nicholas Schmerr/Handout via Reuters)

Mars is Earth's next-door neighbor in the solar system - two rocky worlds with differences down to their very core, literally.

A new study based on seismic data obtained by NASA's robotic InSight lander is offering a fuller understanding of the Martian deep interior and fresh details about dissimilarities between Earth, the third planet from the sun, and Mars, the fourth.

The research, informed by the first detection of seismic waves traveling through the core of a planet other than Earth, showed that the innermost layer of Mars is slightly smaller and denser than previously known. It also provided the best assessment to date of the composition of the Martian core.

Both planets possess cores comprised primarily of liquid iron. But about 20% of the Martian core is made up of elements lighter than iron - mostly sulfur, but also oxygen, carbon and a dash of hydrogen, the study found. That is about double the percentage of such elements in Earth's core, meaning the Martian core is considerably less dense than our planet's core - though more dense than a 2021 estimate based on a different type of data from the now-retired InSight.

"The deepest regions of Earth and Mars have different compositions - likely a product both of the conditions and processes at work when the planets formed and of the material they are made from," said seismologist Jessica Irving of the University of Bristol in England, lead author of the study published this week in the journal Proceedings of the National Academy of Sciences.

The study also refined the size of the Martian core, finding it has a diameter of about 2,212-2,249 miles (3,560-3,620 km), approximately 12-31 miles (20-50 km) smaller than previously estimated. The Martian core makes up a slightly smaller percentage of the planet's diameter than does Earth's core.

The nature of the core can play a role in governing whether a rocky planet or moon could harbor life. The core, for instance, is instrumental in generating Earth's magnetic field that shields the planet from harmful solar and cosmic particle radiation.

"On planets and moons like Earth, there are silicate - rocky - outer layers and an iron-dominated metallic core. One of the most important ways a core can impact habitability is to generate a planetary dynamo," Irving said.

"Earth's core does this but Mars' core does not - though it used to, billions of years ago. Mars' core likely no longer has the energetic, turbulent motion which is needed to generate such a field," Irving added.

Mars has a diameter of about 4,212 miles (6,779 km), compared to Earth's diameter of about 7,918 miles (12,742 km), and Earth is almost seven times larger in total volume.

The behavior of seismic waves traveling through a planet can reveal details about its interior structure. The new findings stem from two seismic events that occurred on the opposite side of Mars from where the InSight lander - and specifically its seismometer device - sat on the planet's surface.

The first was an August 2021 marsquake centered close to Valles Marineris, the solar system's largest canyon. The second was a September 2021 meteorite impact that left a crater of about 425 feet (130 meters).

The US space agency formally retired InSight in December after four years of operations, with an accumulation of dust preventing its solar-powered batteries from recharging.

"The InSight mission has been fantastically successful in helping us decipher the structure and conditions of the planet's interior," University of Maryland geophysicist and study co-author Vedran Lekic said. "Deploying a network of seismometers on Mars would lead to even more discoveries and help us understand the planet as a system, which we cannot do by just looking at its surface from orbit."

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Cutting Off Rhinos' Horns is a Contentious Last Resort to Stop Poaching. New Study Found it Works

A de-horned rhino grazes in South Africa's Pilanesberg National Park, Feb. 25, 2025. (AP Photo/Jerome Delay)
A de-horned rhino grazes in South Africa's Pilanesberg National Park, Feb. 25, 2025. (AP Photo/Jerome Delay)
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Cutting Off Rhinos' Horns is a Contentious Last Resort to Stop Poaching. New Study Found it Works

A de-horned rhino grazes in South Africa's Pilanesberg National Park, Feb. 25, 2025. (AP Photo/Jerome Delay)
A de-horned rhino grazes in South Africa's Pilanesberg National Park, Feb. 25, 2025. (AP Photo/Jerome Delay)

Cutting off the horns of sedated rhinos with a chainsaw has been viewed by wildlife conservationists in Africa for more than 30 years as a necessary evil to save the iconic endangered species from poaching.

They hoped the drastic action was working, but evidence was scarce.

Now, a study published Thursday in the academic journal Science has found that dehorning rhinos has led to a large reduction in poaching in game reserves in and around the Kruger National Park in northern South Africa — an area that's home to 25% of the world's rhinos and is especially vulnerable to poaching.

The results of the seven-year study that ended in 2023 are seen as long-awaited evidence that removing rhinos' horns — which needs to be done every one to two years because they grow back — helps them survive, even if the animals lose part of their makeup.

Consistently reduced poaching The conclusions seem obvious. Lucrative illegal markets in parts of southeast Asia and China crave rhino horns for use in traditional medicines, and removing the rhinos' horns take away what poachers are after.

But Tim Kuiper, a biodiversity scientist at South Africa's Nelson Mandela University and the lead author of the study, said it was new to have long-term data from multiple sites on dehorning rhinos. He said the study, conducted between January 2017 and December 2023, focused on 11 reserves in the Kruger area and compared data from eight that dehorned their rhinos against the three that didn't.

It also analyzed data from the reserves before and after they dehorned their rhinos.

The study showed that dehorning consistently reduced poaching, Kuiper said. It found that the dehorning of more than 2,000 rhinos resulted in a 78% reduction in poaching in those eight reserves, providing some confirmation that such an invasive intervention was worth it.

“It is a big part of what a rhino is, having a horn,” The Associated Press quoted Kuiper as saying. “So having to remove it is kind of a necessary evil, if I can put it that way. But it’s very effective. There’s no doubt it saved hundreds of rhinos' lives.”

South Africa has the largest numbers of black and white rhinos. Namibia, Zimbabwe and Kenya also have significant populations. There are around 17,500 white rhinos and 6,500 black rhinos left in the world, with black rhino numbers reduced from 70,000 in 1970 to less than 2,500 by the time poaching reached a crisis point in the mid-1990s, according to the Save the Rhino organization.

Dehorning was not always accepted Dehorning rhinos started in southern Africa as early as 1989. It has not been accepted without question.

There has been opposition from animal rights activists but also questions from conservationists over what impact it has on a rhino's wellbeing, and what a future might look like with more hornless rhinos.

Vanessa Duthe, a rhino researcher in South Africa not involved in the study, said rhinos use their horns to defend themselves against predators, to compete for territory and, in the case of black rhinos, to look for food. There is also evidence that dehorned rhinos adjust their movements to live in smaller ranges, she said.

She said conservationists don't know the full impacts of dehorning, but research had found it had no adverse effect on rhinos' breeding rates or mortality rates.

“What we do know is that the benefits of dehorning by far outweigh any ecological cost that we’re aware of today,” Duthe said. She said dehorning a rhino now takes around 10 minutes and the process causes minimum distress.

Blindfolds and earmuffs are put on sedated rhinos during dehorning, which also provides an opportunity to microchip rhinos and collect samples that aid research.

Only one part of the battle Conservationists agree that dehorning alone will not end rhino poaching and Kuiper said he saw it as a short-to-mid-term solution.

Other efforts like more effective law enforcement and better support for game rangers on the frontline are key.

While South Africa has helped pull rhinos back from the threat of extinction, more than 400 rhinos a year are still killed by poachers in the country.

The dehorning study was a collaboration between scientists from three South African universities, Oxford University in England and game reserve managers and rangers. It also involved the South African National Parks department, the World Wildlife Fund and the Rhino Recovery Fund.