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 ›
Here's the science of black holes, from supermassive monsters to ones the size of ping-pong balls.
- There's more than one way to make a black hole, says NASA's Michelle Thaller. They're not always formed from dead stars. For example, there are teeny tiny black holes all around us, the result of high-energy cosmic rays slamming into our atmosphere with enough force to cram matter together so densely that no light can escape.
- CERN is trying to create artificial black holes right now, but don't worry, it's not dangerous. Scientists there are attempting to smash two particles together with such intensity that it creates a black hole that would live for just a millionth of a second.
- Thaller uses a brilliant analogy involving a rubber sheet, a marble, and an elephant to explain why different black holes have varying densities. Watch and learn!
- Bonus fact: If the Earth became a black hole, it would be crushed to the size of a ping-pong ball.
Protected animals are feared to be headed for the black market.
In a breakthrough for nuclear fusion research, scientists at China's Experimental Advanced Superconducting Tokamak (EAST) reactor have produced temperatures necessary for nuclear fusion on Earth.
- The EAST reactor was able to heat hydrogen to temperatures exceeding 100 million degrees Celsius.
- Nuclear fusion could someday provide the planet with a virtually limitless supply of clean energy.
- Still, scientists have many other obstacles to pass before fusion technology becomes a viable energy source.
SMARTER FASTER trademarks owned by The Big Think, Inc. All rights reserved.