. 24/7 Space News .
EXO WORLDS
Radioactive elements may be crucial to the habitability of rocky planets
by Staff Writers
Santa Cruz CA (SPX) Nov 11, 2020

These illustrations show three versions of a rocky planet with different amounts of internal heating from radioactive elements. The middle planet is Earth-like, with plate tectonics and an internal dynamo generating a magnetic field. The top planet, with more radiogenic heating, has extreme volcanism but no dynamo or magnetic field. The bottom planet, with less radiogenic heating, is geologically 'dead,' with no volcanism.

The amount of long-lived radioactive elements incorporated into a rocky planet as it forms may be a crucial factor in determining its future habitability, according to a new study by an interdisciplinary team of scientists at UC Santa Cruz.

That's because internal heating from the radioactive decay of the heavy elements thorium and uranium drives plate tectonics and may be necessary for the planet to generate a magnetic field. Earth's magnetic field protects the planet from solar winds and cosmic rays.

Convection in Earth's molten metallic core creates an internal dynamo (the "geodynamo") that generates the planet's magnetic field. Earth's supply of radioactive elements provides more than enough internal heating to generate a persistent geodynamo, according to Francis Nimmo, professor of Earth and planetary sciences at UC Santa Cruz and first author of a paper on the new findings, published November 10 in Astrophysical Journal Letters.

"What we realized was that different planets accumulate different amounts of these radioactive elements that ultimately power geological activity and the magnetic field," Nimmo explained. "So we took a model of the Earth and dialed the amount of internal radiogenic heat production up and down to see what happens."

What they found is that if the radiogenic heating is more than the Earth's, the planet can't permanently sustain a dynamo, as Earth has done. That happens because most of the thorium and uranium end up in the mantle, and too much heat in the mantle acts as an insulator, preventing the molten core from losing heat fast enough to generate the convective motions that produce the magnetic field.

With more radiogenic internal heating, the planet also has much more volcanic activity, which could produce frequent mass extinction events. On the other hand, too little radioactive heat results in no volcanism and a geologically "dead" planet.

"Just by changing this one variable, you sweep through these different scenarios, from geologically dead to Earth-like to extremely volcanic without a dynamo," Nimmo said, adding that these findings warrant more detailed studies.

"Now that we see the important implications of varying the amount of radiogenic heating, the simplified model that we used should be checked by more detailed calculations," he said.

A planetary dynamo has been tied to habitability in several ways, according to Natalie Batalha, a professor of astronomy and astrophysics whose Astrobiology Initiative at UC Santa Cruz sparked the interdisciplinary collaboration that led to this paper.

"It has long been speculated that internal heating drives plate tectonics, which creates carbon cycling and geological activity like volcanism, which produces an atmosphere," Batalha explained. "And the ability to retain an atmosphere is related to the magnetic field, which is also driven by internal heating."

Coauthor Joel Primack, a professor emeritus of physics, explained that stellar winds, which are fast-moving flows of material ejected from stars, can steadily erode a planet's atmosphere if it has no magnetic field.

"The lack of a magnetic field is apparently part of the reason, along with its lower gravity, why Mars has a very thin atmosphere," he said. "It used to have a thicker atmosphere, and for a while it had surface water. Without the protection of a magnetic field, much more radiation gets through and the surface of the planet also becomes less habitable."

Primack noted that the heavy elements crucial to radiogenic heating are created during mergers of neutron stars, which are extremely rare events. The creation of these so-called r-process elements during neutron-star mergers has been a focus of research by coauthor Enrico Ramirez-Ruiz, professor of astronomy and astrophysics.

"We would expect considerable variability in the amounts of these elements incorporated into stars and planets, because it depends on how close the matter that formed them was to where these rare events occurred in the galaxy," Primack said.

Astronomers can use spectroscopy to measure the abundance of different elements in stars, and the compositions of planets are expected to be similar to those of the stars they orbit. The rare earth element europium, which is readily observed in stellar spectra, is created by the same process that makes the two longest-lived radioactive elements, thorium and uranium, so europium can be used as a tracer to study the variability of those elements in our galaxy's stars and planets.

Astronomers have obtained europium measurements for many stars in our galactic neighborhood. Nimmo was able use those measurements to establish a natural range of inputs to his models of radiogenic heating. The sun's composition is in the middle of that range. According to Primack, many stars have half as much europium compared to magnesium as the sun, and many stars have up to two times more than the sun.

The importance and variability of radiogenic heating opens up many new questions for astrobiologists, Batalha said.

"It's a complex story, because both extremes have implications for habitability. You need enough radiogenic heating to sustain plate tectonics but not so much that you shut down the magnetic dynamo," she said. "Ultimately, we're looking for the most likely abodes of life. The abundance of uranium and thorium appear to be key factors, possibly even another dimension for defining a Goldilocks planet."

Using europium measurements of their stars to identify planetary systems with different amounts of radiogenic elements, astronomers can start looking for differences between the planets in those systems, Nimmo said, especially once the James Webb Space Telescope is deployed. "The James Webb Space Telescope will be a powerful tool for the characterization of exoplanet atmospheres," he said.

Research paper


Related Links
University Of California - Santa Cruz
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth


Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Monthly Supporter
$5+ Billed Monthly


paypal only
SpaceDaily Contributor
$5 Billed Once


credit card or paypal


EXO WORLDS
New exoplanet model tells astronomers where to look using 4 simple variables
Tucson AZ (The Conversation) Nov 10, 2020
Only 12 light years from Earth, Tau Ceti is the closest single star similar to the Sun and an all-time favorite in sci-fi stories. Habitable worlds orbiting Tau Ceti were destinations of fictional starships like "The Expanse"'s Nauvoo and "Barbarella"'s vessel. "Star Trek"'s Captain Picard also frequented an exotic bar in the system. Now, thanks to a new approach to analyzing nearby planetary systems, we have a deeper understanding of the actual worlds that orbit Tau Ceti and many other nearby stars. ... read more

Comment using your Disqus, Facebook, Google or Twitter login.



Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

EXO WORLDS
New NASA Partnerships to Mature Commercial Space Technologies, Capabilities

Chinese vision of 'community of shared future for mankind' included in UN outer space resolution again

Air leaking crack in ISS Russian module might get repaired in December

Astronauts prepare for most crowded space station in years

EXO WORLDS
NASA's SpaceX Crew-1 Astronauts Touch Down at Florida Spaceport

Astronauts arrive in Florida for historic launch Saturday

Long March 6 deploys 10 Argentine satellites

PSLV launches EOS-01 and nine customer satellites from Sriharikota

EXO WORLDS
Review board says NASA, ESA ready to pursue Mars sample return mission

Clay subsoil at Earth's driest place may signal life on Mars

Water on ancient Mars

Geologists simulate soil conditions to help grow plants on Mars

EXO WORLDS
China Focus: 18 reserve astronauts selected for China's manned space program

State-owned space giant prepares for giant step in space

China's Xichang launch center to carry out 10 missions by end of March

Eighteen new astronauts chosen for China's space station mission

EXO WORLDS
Successful launch of Kleos Space Scouting Mission satellites into 37 degree Inclined Orbit

Lacuna Space continues to grow IoT constellation with an equatorial satellite

Lift-off for new generation of space scientists

Marking five years of Hungary in ESA

EXO WORLDS
Optimizing the design of new materials

Exceptional ground and flight demonstrations lead way to further applicability across programs

Monitoring open-cast mines better than before

3D print experts discover how to make tomorrow's technology using ink-jet printed graphene

EXO WORLDS
Maunakea telescopes confirm first brown dwarf discovered by radio observations

Water may be naturally occurring on all rocky planets

NYUAD study finds stellar flares can lead to the diminishment of a planet's habitability

Stars and planets grow up together as siblings

EXO WORLDS
Radiation Does a Bright Number on Jupiter's Moon

New plans afoot beyond Pluto

Where were Jupiter and Saturn born?

NASA's Webb To Examine Objects in the Graveyard of the Solar System









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.