Researchers find new information about Earth's origins

Oct 05, 2006
Mukul Sharma and Rasmus Andreasen (Joseph Mehling '69)
Mukul Sharma and Rasmus Andreasen (Joseph Mehling '69)

Two Dartmouth researchers have learned more about the origins and makeup of the solar nebula, the large gaseous cloud thought to have spawned the solar system. Mukul Sharma, assistant professor of Earth sciences, and graduate student Rasmus Andreasen, have found evidence that more than one dying star, or supernova, contributed to the makeup of the solar nebula, which in turn, provides insights into the evolution of planets and asteroids soon after their birth some 4,500 million years ago.

Their study appears in Science Express, the advance online publication of the journal Science, on October 5, 2006.

"Supernovae are dying stars that burst with tremendous energy creating new isotopes and throwing a huge amount of material into interstellar space," says Sharma. "There are two mechanisms that forge isotopes in a supernova-some are produced by high temperature disintegration of previously existing isotopes and others by neutron-induced transmutations.

It has been commonly thought that a single type of supernova supplied isotopes to the primordial soup that was the hot and spinning solar nebula. By investigating the samarium and neodymium isotopic composition of primitive meteorites, which are building blocks of planets, we find that those isotopes that were produced by high temperature disintegration did not mix well in the solar nebula while those generated by neutron-induced transmutations did."

This finding led the researchers to conclude that there was more than one type of supernova matter. A possible reason for a sluggish mixing in the solar nebula is the increase in the grain size from the sun outwards, which then would affect how isotopes were absorbed on the surfaces of grains.

This research also has a bearing on using the samarium and neodymium isotopes in meteorites as way to understand the evolution of Earth and other planets. The researchers found that carbonaceous stony meteorites that come from the distant edge of the asteroid belt possess a distinct blend of samarium and neodymium isotopes in comparison with the stony meteorites with little carbon, an asteroid called 4 Vesta, and the Moon.

"This suggests that the isotopic composition of the Earth prior to any evolutionary modifications should be akin to these carbon-poor meteorites," says Sharma. "However there is a small but resolvable gap between the neodymium isotopic composition of the Earth's upper mantle and the presumed composition of the entire Earth. This indicates that there was formation of continents on Earth within a few million years after its birth. The neodymium isotopes are telling us that these continents are buried somewhere on Earth and hidden from direct observation."

Source: Dartmouth College

Explore further: NASA balloons begin flying in Antarctica for 2014 campaign

add to favorites email to friend print save as pdf

Related Stories

How photosynthesis changed the planet

Nov 20, 2014

Two and a half billion years ago, single-celled organisms called cyanobacteria harnessed sunlight to split water molecules, producing energy to power their cells and releasing oxygen into an atmosphere that ...

What Philae did in its 60 hours on Comet 67P

Nov 18, 2014

The drama of Philae's slow fall, bounce and unfortunate slide into hibernation was one of the most thrilling science stories of a generation. But what in its short 60 hours of life on Comet 67P did it achieve?

Rosetta: What happens next?

Nov 14, 2014

A University of Leicester planetary scientist has hailed the European Space Agency's mission to land a probe on a fast-moving comet as a success despite issues with the landing.

Comet lander may not be securely anchored: ESA

Nov 12, 2014

A European probe Wednesday made the first-ever landing on a comet in a quest to explore the origins of the Solar System, but there were concerns over whether it was fastened securely enough to carry out ...

Recommended for you

Scientists make strides in tsunami warning since 2004

Dec 19, 2014

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

Dec 19, 2014

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.