Earth used to be purple, new NASA study shows
NASA research finds a new direction in searching for signs of life in the Universe.
- NASA-funded research says retinal, not chlorophyll, gave the early Earth its color
- The two pigments co-evolved but retinal came first
- We should be looking for retinal-based life throughout the Universe
Earth used to be a color the late musician Prince would approve of - a shade of purple. Such is the intriguing possibility raised by new NASA-supported research which says a purple-tinged molecule called "retinal" likely gave the early Earth a distinct look. The idea also gives us a potential new direction in the search for planets similar to ours.
If you walk outside, chances are, you'll see a lot of green - sorry, desert-dwelling readers. This green found in nature is the result of photosynthesis - the process by which plants convert energy coming from the sun into useful chemical energy they need to live while producing oxygen for the rest of us. A key part of this process is the pigment chlorophyll which gives plants their green color. It absorbs energy from sunlight and uses it to convert carbon dioxide and water into sugars.
Now a new study argues that retinal likely preceded chlorophyll as the dominant sunlight-absorbing molecule. The scientists focused their attention on retinal-containing proteins, especially ones like bacteriorhodopsin that absorb sunlight in the range inaccessible to chlorophyll. The biologists propose that retinal and chlorophyll co-evolved together, but that retinal likely came first because it's simpler molecule.
Since retinal pigments absorb green and yellow light while transmitting red and blue, life that's based on retinal would look purple. Hence, it's possible that there was a stage of our planet's history that the researchers dubbed "Purple Earth". That time would date somewhere between 2.4 to 3.5 billion years ago, prior to the Great Oxygenation Event, which was likely due to the rise chlorophyll-based photosynthesis.
The study comes from Shiladitya DasSarma, Professor of molecular biology at the University of Maryland, and Dr. Edward Schwieterman, an astrobiologist at the University of California, Riverside.
"Retinal-based phototrophic metabolisms are still prevalent throughout the world, especially in the oceans, and represent one of the most important bioenergetic processes on Earth," said DasSarma to Astrobiology Magazine.
Purple microorganisms and purple membrane. (a) Australian salt pond with a bloom of purple microorganisms (Courtesy Cheetham Salt Co.). (b) Sucrose gradient separating Halobacterium sp. cell lysate, including both red (upper) and purple (lower) pigments (Credit: Victoria Laye and Priya DasSarma).
Another interesting aspect of the paper is that if Earth had a retinal stage and since retinal is a simpler molecule than chlorophyll, then it stands to reason that we should take this into account when looking for new inhabitable (or already inhabited) planets. In fact, it's entirely possible that retinal-based life could be more widespread throughout the Universe.
From the counter-intuitive standpoint of color wavelengths viewed through a spectroscope, we should be looking for a "green edge" in a planet's spectrum to spot retinal biosignatures, say the researchers.
Check out the new paper "Early evolution of purple retinal pigments on Earth and implications for exoplanet biosignatures" in the International Journal of Astrobiology. It was supported by NASA Astrobiology.
- NASA's Mars Curiosity Rover found new clues about alien life ... ›
- NASA Finds Ancient Organic Material, Mysterious Methane on Mars ... ›
- News | New Clues to Compositions of TRAPPIST-1 Planets ›
- NASA's Mars Rover Curiosity Finds Carbon 'Building Blocks of Life' ›
- Curiosity Rover Finds Ancient 'Building Blocks for Life' on Mars ›
- NASA GISS: NASA News & Feature Releases ›
- Two telescopes reveal new clues to TRAPPIST-1 planet ... ›
- A New Clue in the Search for Forests on Distant Planets ›
- Life Signs | The Search for Life – Exoplanet Exploration: Planets ... ›
- Our Living Planet Shapes the Search for Life Beyond Earth | NASA ›
- Earth used to be purple and once had two moons - YouTube ›
- Characterizing the purple Earth: Modelling the globally-integrated ... ›
- When The Earth Was Purple - YouTube ›
- What purple can tell us about life on other planets - CNN ›
- Early Earth Was Purple, Study Suggests ›
Malcolm Gladwell teaches "Get over yourself and get to work" for Big Think Edge.
- Learn to recognize failure and know the big difference between panicking and choking.
- At Big Think Edge, Malcolm Gladwell teaches how to check your inner critic and get clear on what failure is.
- Subscribe to Big Think Edge before we launch on March 30 to get 20% off monthly and annual memberships.
We take fewer mental pictures per second.
- Recent memories run in our brains like sped-up old movies.
- In childhood, we capture images in our memory much more quickly.
- The complexities of grownup neural pathways are no match for the direct routes of young brains.
It's not just a case of "what doesn't kill you makes you stronger."
- A new study suggests children who endure trauma grow up to be adults with more empathy than others.
- The effect is not universal, however. Only one kind of empathy was greatly effected.
- The study may lead to further investigations into how people cope with trauma and lead to new ways to help victims bounce back.
It's one of the most consistent patterns in the unviverse. What causes it?
- Spinning discs are everywhere – just look at our solar system, the rings of Saturn, and all the spiral galaxies in the universe.
- Spinning discs are the result of two things: The force of gravity and a phenomenon in physics called the conservation of angular momentum.
- Gravity brings matter together; the closer the matter gets, the more it accelerates – much like an ice skater who spins faster and faster the closer their arms get to their body. Then, this spinning cloud collapses due to up and down and diagonal collisions that cancel each other out until the only motion they have in common is the spin – and voila: A flat disc.
SMARTER FASTER trademarks owned by The Big Think, Inc. All rights reserved.