Evolution Archives

April 9, 2009December 24, 2015 by Anne Minard

Without Nickel, Life on Earth Could Finally Breathe

Caption: Banded iron formations like this from northern Michigan contain evidence of a drop in dissolved nickel in ancient oceans. Credit: Carnegie Institution for Science

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Researchers have long puzzled over why oxygen flourished in Earth’s atmosphere starting around 2.4 billion years.

Called the “Great Oxidation Event,” the transition “irreversibly changed surface environments on Earth and ultimately made advanced life possible,” said Dominic Papineau of the Carnegie Institution’s Geophysical Laboratory.

Now, Papineau has co-authored a new study in the journal Nature, which reveals new clues to the mystery in ancient sedimentary rocks.

The research team, led by Kurt Konhauser of the University of Alberta in Edmonton, analyzed the trace element composition of sedimentary rocks known as banded-iron formations, or BIFs, from dozens of different localities around the world, ranging in age from 3,800 to 550 million years. Banded iron formations are unique, water-laid deposits often found in extremely old rock strata that formed before the atmosphere or oceans contained abundant oxygen. As their name implies, they are made of alternating bands of iron and silicate minerals.

They also contain minor amounts of nickel and other trace elements. And the history of nickel, the researchers think, may reveal a secret to the origin of modern life.

Nickel exists in today’s oceans in trace amounts, but was up to 400 times more abundant in the Earth’s primordial oceans. Methane-producing microorganisms, called methanogens, thrive in such environments, and the methane they released to the atmosphere might have prevented the buildup of oxygen gas, which would have reacted with the methane to produce carbon dioxide and water.

A drop in nickel concentration would have led to a “nickel famine” for the methanogens, who rely on nickel-based enzymes for key metabolic processes. Algae and other organisms that release oxygen during photosynthesis use different enzymes, and so would have been less affected by the nickel famine. As a result, atmospheric methane would have declined, and the conditions for the rise of oxygen would have been set in place.

The researchers found that nickel levels in the BIFs began dropping around 2.7 billion years ago and by 2.5 billion years ago was about half its earlier value.

“The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event,” Papineau said. “And from what we know about living methanogens, lower levels of nickel would have severely cut back methane production.”

As for why nickel dropped in the first place, the researchers point to geology. During earlier phases of the Earth’s history, while its mantle was extremely hot, lavas from volcanic eruptions would have been relatively high in nickel. Erosion would have washed the nickel into the sea, keeping levels high. But as the mantle cooled, and the chemistry of lavas changed, volcanoes spewed out less nickel, and less would have found its way to the sea.

“The nickel connection was not something anyone had considered before,” Papineau said. “It’s just a trace element in seawater, but our study indicates that it may have had a huge impact on the Earth’s environment and on the history of life.”

Source: Carnegie Institution for Science, via Eurekalert.

February 21, 2009December 24, 2015 by Anne Minard

Arizona Scientist: We Could All Be Martians

Artist's conception of an fragment as it blasts off from Mars. Boulder-sized planetary fragments could be a mechanism that carried life between Mars and Earth, UA planetary scientist Jay Melosh says. (Credit: The Planetary Society)

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As long as we’re still pondering human origins, we may as well entertain the idea that our ancestor microbes came from Mars.

And Jay Melosh, a planetary scientist from the University of Arizona in Tucson, is ready with a geologically plausible explanation.

Meteorites.

“Biological exchange between the planets of our solar system seem not only possible, but inevitable,” because of meteorite exchanges between the planets, Melosh said. “Life could have originated on the planet Mars and then traveled to Earth.”

jay_melosh — Jay Melosh. Credit: Maria Schuchardt, University of Arizona Lunar and Planetary Lab

Melosh is a long-time researcher who says he’s studied “geological violence in all its forms.” He helped forge the giant impact theory of the moon’s formation, and helped advance the theory that an impact led to the extinction of the dinosaurs 65 million years ago.

He points out that Martian meteorites have been routinely pummeling Earth for billions of years, which would have opened the door for past Mars microbes to hitch a ride. Less regularly, Earth has undergone impacts that sent terrestrial materials flying, and some of those could have carried microbes toward the Red Planet.

“The mechanism by which large impacts on Mars can launch boulder-sized surface rocks into space is now clear,” he said. He explained that a shock wave spreads away from an impact site faster than the speed of sound, interacting with the planetary surface in a way that allows material to be cast off – at relatively low pressure, but high speed.

“Lightly damaged material at very high speeds,” he said, “is the kind of environment where microorganisms can survive.”

Scientists have recent evidence of Earth microbes surviving a few years in space. When the Apollo 12 astronauts landed on the moon, they retrieved a camera from Surveyor 3, an unmanned lander that had touched down nearly three years prior. Earthly microbes – including those associated with the common cold — were still living inside the camera box.

“The records were good enough to show one of the technicians had a cold when he was working on it,” he said.

Scientists also have evidence that microbes can survive for thousands or even hundreds of thousands of years when frozen on Earth, but surviving that long in space would be an entirely different matter, with the bombardment of UV light and cosmic rays. Then again, the microbe Dienococcus radiodurans is known to survive in the cores of nuclear reactors.

Melosh acknowledges that scientists lack proof that such an exchange has actually occurred between Mars and Earth — but science is getting ever closer to being able to track it down.

LEAD PHOTO CAPTION: Artist’s conception of an fragment as it blasts off from Mars. Boulder-sized planetary fragments could be a mechanism that carried life between Mars and Earth, UA planetary scientist Jay Melosh says. (Painting by Don Davis. Copyright SETI Institute, 1994)

Source: University of Arizona and an interview with Jay Melosh

July 28, 2008December 24, 2015 by Ian O'Neill

US Signs International Deal to Collaborate on Lunar Missions

Astronaut Eugene Cernan from Apollo 17, the last mission to the Moon (NASA)

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NASA has signed a landmark agreement to collaborate with emerging space-faring nations for the exploration of the Moon. This collaboration will include Canada, Germany, India, Italy, Japan, South Korea, Britain and France in the aim to work with NASA developing new technologies and send a series of robotic exploratory missions to pave the way for a manned return mission. The director of NASA’s planetary science division points out that these eight member states are keen to send their first astronauts to the lunar surface. Whilst some may view this collaboration as an attempt by NASA to ‘spread the cost’ of space travel (especially in the current climate of budget cuts), the main point of this deal is to make manned missions to the Moon more of an international effort. This will give smaller space agencies more opportunities, boost the quality of the science that can be achieved and possibly lead us to some answers about how life formed on Earth 4 billion years ago…

The deal was brokered at NASA’s Ames Research Center, Moffett Field, California, last Thursday, and it is expected to be finalized tomorrow. The meeting took place during the largest Moon-specific conference since the US Apollo missions, highlighting the recent drive to get man back to the lunar surface. NASA had already allocated significant funding toward four manned landers, but scientists have asked for eight, so an international collaboration is required so adequate science can be carried out.

At the centre of this renewed vigour is the quest to understand how life was kick-started on Earth. From recent analysis of Apollo rocks brought back to Earth in the 1970’s, it is thought that the early Solar System was a violent place. Scientists believe this planetary chaos may be the root cause of life on Earth; analysing the lunar surface is critical so a better picture may be created of the Earth-Moon system billions of years ago.

“What’s happening right now is that a revolution in planetary science is going on. We are taking these small pieces and we are starting to put together the puzzle, and we are surprised by what we find.” – James Green, Director of NASA’s Planetary Science Division.

Why is the Moon so special anyway? Surely most of the answers can be found down here on Earth? Well, that’s not entirely correct. The Moon is an open history book of the Solar System’s evolution. Its surface has not been altered by plate tectonics, volcanoes or atmospheric erosion processes (unlike the terrestrial surface); ancient events are etched in its rock, waiting to be read by future lunar explorers. This was the conclusion reached by National Research Council of the National Academy of Sciences last year. From the evidence stored in lunar rock, it is hoped that the “terminal cataclysm hypothesis” may be proven or disproved. This theory suggests that Uranus and Neptune once orbited within the orbit of Jupiter. The cataclysm occurred when the powerful Jovian gravitational field flung the smaller gas giants to the outer reaches of the Solar System.

But where is the Earth-Moon connection? This turmoil in the Solar System will have displaced huge numbers of asteroids and comets, scattering them toward the inner planets. This event may have been the trigger of the “late heavy bombardment” between 3.8 to 4 billion years ago which coincided with the formation of life on Earth. This period of time can be studied in great depth on the Moon.

This increased interest in lunar science and the emergence of Japan, China and India create an opportunity NASA will not want to miss. This new international collaboration may be exactly what NASA needs to invigorate funding and help us understand how life was sparked on our blue planet.

Source: Mercury News

August 9, 2007December 26, 2015 by Fraser Cain

An Experiment to Test Panspermia

One of most intriguing, and controversial, theories astrobiology is the concept of Panspermia. This idea proposes that life on Earth might have began on another planet, or maybe even out in interstellar space. Scientists have discovered just how hardy microbial life can be, surviving long journeys in the vacuum, cold, and radiation of space. Now an experiment has been devised to see how well microbes can withstand reentry through the Earth’s atmosphere.

The experiment, designed by Professor John Parnell from the University of Aberdeen, involves bolting a Scottish rock to the outside of an ESA research spacecraft. When the Foton M3 mission launches on Friday, September 14th, microbes in the rock will enjoy the acceleration of liftoff, 12 days of microgravity and vacuum, and then re-entry through the Earth’s atmosphere.

“The objective behind this is to look at the rock’s behaviour when it is exposed during re-entry through the Earth’s atmosphere – when temperatures are extreme. This will tell us something about the likelihood of life being transferred between planets on meteorites.

“The Orkney rock is a very robust material but it will be interesting to see if organic matter in the rock is robust enough to survive the harsh conditions endured during re-entering the Earth’s atmosphere.”

In theory, asteroid strikes in the past excavated material on other planets, hurling microbe-laden rocks into interplanetary space. The rocks would then act as lifeboats, carrying the microbes to other planets. More importantly, they should protect the bacteria as the rock plunges into the atmosphere.

This experiment will help discover if there’s anything to this idea. Bacteria might just be hardy enough to survive the complete journey from planet to planet.

Original Source:Univ. Of Aberdeen

October 13, 2006June 5, 2022 by R. Jay Gabany

Astrophoto: Swan Song for a Comet

On December 2, 1995, the SOHO (Solar and Heliospheric Observatory) spacecraft was launched aboard an Atlas/Centaur rocket from Cape Canaveral Air Station on a two-year mission to monitor the sun. Almost eleven years later, the SOHO spacecraft continues to faithfully record solar activity orbiting the Sun about 1.5-million kilometers inward from Earth. NASA and the European Space Agency operate the satellite jointly. Everyday, SOHO transmits pictures that are freely available for viewing on the Internet. These images inform scientists around the world about the Sun’s nature and behavior. Its images and data enable them to predict “space weather” events affecting our planet. Earlier in July of this year, someone discovered a new comet in a SOHO picture and now it’s gracing our evening skies as seen in this telescopic image.
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