life on Earth Archives

July 31, 2014December 23, 2015 by Elizabeth Howell

This Model Of Earth’s Giant Impacts Makes Us Wonder How Life Arose

Artist's conception of early Earth after several large asteroid impacts, moving magma on to the surface. Credit: Simone Marchi/SwRI

In case you need a reminder that the solar system was a harsh place to grow up, the early Earth looks like it was in the middle of a shooting gallery in this model. The map that you see above shows a scenario for where researchers believe asteroids struck our planet about four billion to 4.5 billion years ago, which is very early in the Earth’s five-billion-year history.

The research reveals the surface of the Earth repeatedly being churned by these impacts as the young solar system came together, with small rocks gradually coalescing into planetesimals. Much of the leftover debris peppered the planets, including our own.

“Prior to approximately four billion years ago, no large region of Earth’s surface could have survived untouched by impacts and their effects,” stated Simone Marchi, who led the research and works at the Southwest Research Institute in Colorado.

“The new picture of the Hadean Earth emerging from this work has important implications for its habitability,” added Marchi, who is also senior researcher at NASA’s Solar System Exploration Research Virtual Institute.

In this dangerous early period, the researchers estimate the Earth was smacked by 1-4 asteroids or comets that were more than 600 miles (966 kilometers) wide — enough to wipe out life across the planet. They also believe that between 3-7 impactors were more than 300 miles (482 kilometers) wide, which would evaporate oceans across the world.

“During that time, the lag between major collisions was long enough to allow intervals of more clement conditions, at least on a local scale,” added Marchi. “Any life emerging during the Hadean eon likely needed to be resistant to high temperatures, and could have survived such a violent period in Earth’s history by thriving in niches deep underground or in the ocean’s crust.”

To produce the model, the researchers took a recent model of lunar impacts and applied it to Earth. The moon’s scarred surface helps them estimate what happened on our own planet, they said, because the craters provide an “absolute impactor flux” separate from any models that talk about how the Earth came together. Recall that erosion on the moon is very slow, providing accessible records of things that happened millions or billions of years ago.

The research was published in the journal Nature.

Source: NASA

March 13, 2014December 23, 2015 by Elizabeth Howell

Did Life On Earth As We Know It Come From ‘Geological Life’?

Hydrothermal vents deep in Earth's oceans. Could similar types of vents power the transport of silica and other materials out from Enceladus? Credit: NOAA

When it comes to life on Earth, we’re not sure if it came from the outside (transported by comets) or on the inside. A new theory focuses on the “interior ” theory, saying that microbes could have evolved from non-living matter such as chemical compounds in minerals and gases.

“Before biological life, one could say the early Earth had ‘geological life’. It may seem unusual to consider geology, involving inanimate rocks and minerals, as being alive. But what is life?” stated Terry Kee, a biochemist at the University of Leeds in the United Kingdom who participated in the research.

“Many people have failed to come up with a satisfactory answer to this question. So what we have done instead is to look at what life does, and all life forms use the same chemical processes that occur in a fuel cell to generate their energy.”

When thinking of a car, the research team says, they point out that fuel cells create electrical energy through the reaction of fuels and oxidants. This is called a “redox reaction”, which takes place when a molecule loses electrons and another molecule gains them.

In plants, photosynthesis creates electrical energy when carbon dioxide breaks down into sugars, and water is oxidized into molecular oxygen. (By contrast, humans oxidize sugars into carbon dioxide and break down the oxygen into water — another electrical energy process.)

Now, let’s go a step further. Hydrothermal vents are hot geysers on the sea floor that are often considered an interesting spot for life studies. They host “extremophiles”, or forms of life that exist (“thrive” is the better word) despite a harsh environment. The researchers say these vents are a sort of “environmental fuel cell” because electrical energy is generated from redox reactions between seawater oxidants and hydrothermal vents.

And this is where the new research comes in. At the University of Leeds and NASA’s Jet Propulsion Laboratory, the researchers put iron and nickel in the place of the usual “platinum catalysts” found in fuel cells and electrical experiments.

Rendering showing the location and size of water vapor plumes coming from Europa's south pole. — Rendering showing the location and size of water vapor plumes coming from Europa’s south pole.

While the power was reduced, electricity did indeed flow. And while researchers still don’t know how non-life could have transformed into life, they say this is another step to understanding what happened. What’s more, it could be useful for future trips to other planets.

“These experiments simulate the electrical energy produced in geological systems, so we can also use this to simulate other planetary environments with liquid water, like Jupiter’s moon Europa or early Mars,” stated Laura Barge, a researcher from the NASA Astrobiology Institute* who led the research.

“With these techniques we could actually test whether any given hydrothermal system could produce enough energy to start life, or even, provide energetic habitats where life might still exist and could be detected by future missions.”

You can read about the research in the journal Astrobiology.

Source: University of Leeds

* Disclosure: The author of this article is also a freelancer for the NASA Astrobiology Institute.

January 30, 2014December 23, 2015 by Elizabeth Howell

Earth’s Water Story Gets A Plot Twist From Space Rock Search

Artist's conception of asteroids and a gas giant planet. Credit: Harvard-Smithsonian Center for Astrophysics

We at Universe Today have snow on our minds these days with all this Polar Vortex talk. From out the window, the snowflakes all look the same, but peer at flakes under a microscope and you can see all these different designs pop up. Turns out that our asteroid belt between Mars and Jupiter is also much more diverse than previously believed, all because astronomers took the time to do a detailed survey.

Here’s the interesting thing: the diversity, the team says, implies that Earth-like planets would be hard to find, which could be a blow for astronomers seeking an Earth 2.0 somewhere out in the universe if other research agrees.

To jump back a couple of steps, there’s a debate about how water arose on Earth. One theory is that back billions of years ago when the solar system was settling into its current state — a time when planetesimals were crashing into each other constantly and the larger planets possibly migrated between different orbits — comets and asteroids bearing water crashed into a proto-Earth.

Artist's conception of asteroids or comets bearing water to a proto-Earth. Credit: Harvard-Smithsonian Center for Astrophysics — Artist’s conception of asteroids or comets bearing water to a proto-Earth. Credit: Harvard-Smithsonian Center for Astrophysics

“If true, the stirring provided by migrating planets may have been essential to bringing those asteroids,” the astronomers stated in a press release. “This raises the question of whether an Earth-like exoplanet would also require a rain of asteroids to bring water and make it habitable. If so, then Earth-like worlds might be rarer than we thought.”

To take this example further, the researchers found that the asteroid belt comes from a mix of locations around the solar system. Well, a model the astronomers cite shows that Jupiter once migrated much closer to the sun, basically at the same distance as where Mars is now.

When Jupiter migrated, it disturbed everything in its wake and possibly removed as much as 99.9 per cent of the original asteroid population. And other planet migrations in general threw in rocks from everywhere into the asteroid belt. This means the origin of water in the belt could be more complicated than previously believed.

You can read more details of the survey in the journal Nature. Data was gathered from the Sloan Digital Sky Survey and the research was led by Francesca DeMeo, a Hubble postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics.

Source: Harvard-Smithsonian Center for Astrophysics

October 30, 2013December 23, 2015 by Jason Major

Catastrophic Impacts Made Life on Earth Possible

According to a new study, meteors may be less dangerous than we thought, thanks to Earth's atmosphere. Credit: David A Aguilar (CfA).

How did life on Earth originally develop from random organic compounds into living, evolving cells? It may have relied on impacts by enormous meteorites and comets — the same sort of catastrophic events that helped bring an end to the dinosaurs’ reign 65 million years ago. In fact, ancient impact craters might be precisely where life was able to develop on an otherwise hostile primordial Earth.

This is the hypothesis proposed by Sankar Chaterjee, Horn Professor of Geosciences and the curator of paleontology at the Museum of Texas Tech University.

“This is bigger than finding any dinosaur. This is what we’ve all searched for – the Holy Grail of science,” Chatterjee said.

Our planet wasn’t always the life-friendly “blue marble” that we know and love today. At one point early in its history it was anything but hospitable to life as we know it.

“When the Earth formed some 4.5 billion years ago, it was a sterile planet inhospitable to living organisms,” Chatterjee said. “It was a seething cauldron of erupting volcanoes, raining meteors and hot, noxious gasses. One billion years later, it was a placid, watery planet teeming with microbial life – the ancestors to all living things.”

Exactly how did this transition happen? That’s the Big Question in paleontology, and Chatterjee believes he may have found the answer lying within some of the world’s oldest and largest impact craters.

After studying the environments of the oldest known fossil-containing rocks in Greenland, Australia and South Africa, Chatterjee said these could be remnants of ancient craters and may be the very spots where life began in deep, dark and hot environments — similar to what’s found near thermal vents in today’s oceans.

Larger meteorites that created impact basins of about 350 miles in diameter inadvertently became the perfect crucibles, according to Chatterjee. These meteorites also punched through the Earth’s crust, creating volcanically driven geothermal vents. They also brought the basic building blocks of life that could be concentrated and polymerized in the crater basins.

In addition to new organic compounds — and, in the case of comets, considerable amounts of water — impacting bodies may also have brought the necessary lipids needed to help protect RNA and allow it to develop further.

“RNA molecules are very unstable. In vent environments, they would decompose quickly. Some catalysts, such as simple proteins, were necessary for primitive RNA to replicate and metabolize,” Chatterjee said. “Meteorites brought this fatty lipid material to early Earth.”

How organic compounds in crater basins were encapsulated in lipid membranes and became the first cells (Chatterjee)

Based on research in Australia by University of California professor David Deamer, the ingredients for all-important cell membranes were delivered to Earth via meteorites and existed in water-filled craters.

“This fatty lipid material floated on top of the water surface of crater basins but moved to the bottom by convection currents,” suggests Chatterjee. “At some point in this process during the course of millions of years, this fatty membrane could have encapsulated simple RNA and proteins together like a soap bubble. The RNA and protein molecules begin interacting and communicating. Eventually RNA gave way to DNA – a much more stable compound – and with the development of the genetic code, the first cells divided.”

And the rest, as they say, is history. (Well, biology really, and no small amount of chemistry and paleontology… and some astrophysics… well you get the idea.)

Chatterjee recognizes that further experiments will be needed to help support or refute this hypothesis. He will present his findings Oct. 30 during the 125th Anniversary Annual Meeting of the Geological Society of America in Denver, Colorado.

Source: Texas Tech news article by John Davis