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Bringing Building Blocks of Life to Earth from Space

By David Reneke

New research supports the view that meteorites kickstarted life on Earth, and Australian astronomers have measured how a galaxy’s spin affects its shape.

How life began on Earth, roughly 4 billion years ago, is one of the great scientific questions. New results from scientists at McMaster University and the Max Planck Institute for Astronomy suggest a key role for meteorites landing in warm little ponds, delivering essential organic molecules that kickstarted the emergence of life in the shape of self-replicating RNA molecules.

The astronomers reached their conclusions after assembling models about planet formation, geology, chemistry and biology into a coherent quantitative model for the emergence of life. The most interesting result from these calculations is that life must have emerged fairly early while Earth was still taking shape.

This, they maintain, was only a few hundred million years after the Earth had cooled sufficiently to allow liquid surface water, such as ponds or oceans. The building blocks of life would have been brought to Earth by meteorites during an era when Earth’s bombardment by such small extraterrestrial rocks was much more intense than today.

Astronomers agree that in order to understand the origin of life we need to understand Earth as it was billions of years ago. As this study shows, astronomy provides a vital part of the answer. The details of how our solar system formed have direct consequences for the origin of life on Earth.

The new work supports the “warm little pond” hypotheses for the origin of life, with RNA polymers forming in shallow ponds during cycles in which the pond water evaporates and is refilled periodically. It shows how meteorites could have transported a sufficient amount of nucleotides to thousands of such ponds on Earth, helping to kickstart life in at least one of those ponds. “We have provided plausible physical and chemical information about the conditions under which life could have originated,” said Dmitry Semenov of the Max Planck Institute.

How true! Now it’s the experimentalists’ turn to find out how life could indeed have emerged under these very specific early conditions.

How a Galaxy’s Spin Affects Its Shape

For the first time Australian astronomers have measured how a galaxy’s spin affects its shape. It sounds simple, but measuring a galaxy’s true 3D shape is a tricky problem that astronomers first tried to solve 90 years ago.

“This is the first time we’ve been able to reliably measure how a galaxy’s shape depends on any of its other properties, in this case its rotation speed,” said research team leader Dr Caroline Foster of The University of Sydney, who completed this research while working at the Australian Astronomical Observatory (AAO).

There’s one thing astronomers agree on: galaxies can be shaped like a pancake, a sea urchin, a football, or anything in between. Faster-spinning galaxies are flatter than their slower-spinning siblings, the team found. It’s simply a rule the universe works by.

The team’s findings show that among spiral galaxies, which have discs of stars, the faster-spinning ones have more circular disc shapes. The team made its findings with SAMI, an instrument jointly developed by The University of Sydney and the Australian Astronomical Observatory with funding from the ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO).

SAMI gives detailed information about the movement of gas and stars inside galaxies. This instrument has a wide grasp; it can examine 13 galaxies at a time and thus collect information about huge numbers of them. The result is a bigger data base to work with.

Foster’s team used a sample of 845 galaxies, over three times more than the biggest previous study. This large number was the key to solving the shape problem. Because a galaxy’s shape is the result of past events such as merging with other galaxies, knowing its shape also tells us about the galaxy’s history.

In a way it’s sort of like “archaeo-astronomy” by backtracking on what went before in an effort to understand what we have now. It’s a new study so watch this space!


David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com