The Search for Extraterrestrial Life 19One current focus for exoplanet research is on the way life is known to alters its environment in order to remain in existence — the Gaian Habitable Zone
In our universe:
“Billions of celestial objects revealed in gargantuan survey of the Milky Way”: “The new dataset contains a staggering 3.32 billion celestial objects—arguably the largest such catalog so far”: “Most of the stars and dust in the Milky Way are located in its disk—the bright band stretching across this image—in which the spiral arms lie. While this profusion of stars and dust makes for beautiful images, it also makes the Galactic plane challenging to observe. The dark tendrils of dust seen threading through this image absorb starlight and blot out fainter stars entirely, and the light from diffuse nebulae interferes with any attempts to measure the brightness of individual objects. Another challenge arises from the sheer number of stars, which can overlap in the image and make it difficult to disentangle individual stars from their neighbors.” – Association of Universities for Research in Astronomy (AURA) at Phys.org (January 18, 2023). The paper is open access.
“What Is Our Universe Expanding Into?”: Stony Brook astrophysicist Paul Sutter answers the question asked by Brian Gallagher at Nautilus (January 16, 2023): “Yes, our universe is expanding. Our universe has no center and no edge. The Big Bang didn’t happen in one location in space. The Big Bang happened everywhere in the cosmos simultaneously. The Big Bang was not a point in space. It was a point in time. It exists in all of our paths.” By analogy, he asks, where is the center of the surface of Earth? There isn’t one, of course. Earth could be expanding like an inflating balloon but not from any particular point on its surface. He points out that the universe is three-dimensional, not two-dimensional, which makes the whole thing hard to picture. But the math apparently supports it.
In our galaxy:
Life itself makes planets more habitable, says Stony Brook astrophysicist Paul Sutter: “One of the defining characteristics of life on a planet is its ability to change the equilibrium state of a world. For example, Earth was born with a lot of oxygen in its atmosphere, but that oxygen is unstable. We should have lost it a long time ago, and in fact we did. But photosynthesis from plants and algae replenishes oxygen in our atmosphere, giving us a new oxygen-rich state that we otherwise wouldn’t have had. This concepts extends to other properties of a planetary atmosphere, like its temperature and its pressure. Essentially, life on a planet works to keep everything in balance and as hospitable as possible. A pair of astronomers have recently used in this concept to extend the concept of the Habitable Zone to what they call the Gaian habitable zone – a habitable zone that is modified by life itself.” – Universe Today, (January 13, 2023) The paper on the Gaian habitable zone is open access. This won’t help us understand how life got started but it might help us understand how it stays in existence, despite huge challenges: Life renovates its environment.
Should we be looking for the biosignatures of plants, not animals? “Worlds bustling with plant life should shine in a detectable wavelength of infrared, say exoplanet scientists”: “Earth’s abundant plant life changes our planet’s “light signature.” The change is based on photosynthesis and how plant life absorbs some light frequencies while reflecting others. The resulting phenomenon is called the vegetation red edge (VRE.) Exoplanet scientists have worked on the idea of the VRE as a biosignature for a few years. It’s based on the fact that chlorophyll absorbs light in the visible part of the spectrum and is almost transparent in the infrared. Other cellular structures in the vegetation reflect the infrared. This helps plants avoid overheating during photosynthesis. This absorption and reflection make it possible for remote sensing to gauge plant health, coverage, and activity, and agricultural scientists use it to monitor crops.” – Evan Gough, (Phys.org, January 18, 2023) The paper is open access.
Help wanted: Apply to NASA: “NASA’s Exoplanet Watch Wants Your Help Studying Planets Around Other Stars”: “universities, research institutes, and space agencies have come to rely on citizen scientists in recent years. With the help of online resources, data-sharing, and networking, skilled amateurs can lend their time, energy, and resources to the hunt for planets beyond our Solar System. In recognition of their importance, NASA has launched Exoplanet Watch, a citizen science project sponsored by NASA’s Universe of Learning. This project lets regular people learn about exoplanets and get involved in the discovery and characterization process.” – Matt Williams, Universe Today, (January 14, 2023)
In our solar system:
Right around home:
Moon: Oxygen on the Moon?: “One day, there could be a pipeline of oxygen flowing from the moon’s south pole”: “The lunar south pole contains vast quantities of primordial water ice, frozen solid in the region’s craters where sunlight never reaches it. That ice can be melted and separated into hydrogen and oxygen… Everyone involved in lunar science knows this, and the established idea is that the ice would be processed in situ, and oxygen would be put in cryogenic pressure vessels called dewars and transported to wherever it was needed. Since the equatorial regions have the most sunlight and the most solar energy, that’s likely where lunar bases will be established.” – Evan Gough (Phys.org, January 16, 2023)
Right here at home:
Meteorite with the building blocks of life crash landed on a driveway in Gloucestershire, England in February 2021: “In the study, the analysis found a range of organic matter, which reveals that the meteorite was once from part of an asteroid where liquid water occurred, and if it that asteroid had been given access to the water, a chemical reaction could have occurred leading to more molecules turning into amino acids and protein—the building blocks of life. The Winchcombe meteorite is a rare carbon rich chondritic meteorite (approximately 4% of all recovered meteorites, containing up to 3.5 weight percent of carbon) and is the first ever meteorite of this type to be found in the U.K. with an observed meteorite fall event, with more than 1,000 eyewitnesses and numerous footages of the fireball.” – Royal Holloway/University of London (Phys.org, January 10, 2023) The paper is open access.
Around the water cooler: There’s no planet B, say Arwen E Nicholson and Raphaëlle D Haywood, who are both physicists and astronomers: “The scientific evidence is clear: the only celestial body that can support us is the one we evolved with. Here’s why: … Finding evidence for alien life promises to shake the foundations of our understanding of our own place in the cosmos. But finding alien life does not mean finding another planet that we can move to. Just as life on Earth has evolved with our planet over billions of years, forming a deep, unique relationship that makes the world we see today, any alien life on a distant planet will have a similarly deep and unique bond with its own planet. We can’t expect to be able to crash the party and find a warm welcome.” (Aeon, January 16, 2023) Of course, if there is a party out there, we are bound to crash it and find out who’s right.
More on the universe as fine-tuned for life
From a letter by Steve Meyer’s to Inference Review, in response to an article by physicist Larry Krauss:
Could a different set of physical parameters have enabled the evolution of radically different forms of life? Krauss believes so. Although biologists have found it difficult to agree on a comprehensive definition, they do agree on some things. All forms of life must maintain a boundary; and they must perform integrated sets of complex chemical reactions within that boundary. This is beyond the power of simple hydrogen or helium atoms. Producing atoms more complex than helium requires significant fine-tuning of the cosmological constant, the masses of quarks, and the ratio between the strong nuclear and electromagnetic force. It also requires a universe in which the Pauli exclusion principle constrains the allowable quantum states of fermions. Fine-tuning precedes any biologically relevant process of evolution.Stephen C. Meyer. On Fine-Tuning and Design, Inference Review, (May 2021)
You may also wish to read: The search for extraterrestrial life 18. We are starting to find more different kinds of exoplanets and an unexpected source of water on Mars. Martian meteorite Tissint turns out to have organic magnesium compounds that have not previously been seen on Mars.