Is There a Fundamental Logic to Life?

Will it be possible someday for astrobiologists to search for life "as we don't know it"? Credit: NASA/Jenny Mottar

One of the more daunting questions related to astrobiology—the search for life in the cosmos—concerns the nature of life itself. For over a century, biologists have known that life on Earth comes down to the basic building blocks of DNA, RNA, and amino acids. What’s more, studies of the fossil record have shown that life has been subject to many evolutionary pathways leading to diverse organisms. At the same time, there is ample evidence that convergence and constraints play a strong role in limiting the types of evolutionary domains life can achieve.

For astrobiologists, this naturally raises questions about extraterrestrial life, which is currently constrained by our limited frame of reference. For instance, can scientists predict what life may be like on other planets based on what is known about life here on Earth? An international team led by researchers from the Santa Fe Institute (SFI) addressed these and other questions in a recent paper. After considering case studies across various fields, they conclude that certain fundamental limits prevent some life forms from existing.

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A Young Exoplanet's Atmosphere Doesn't Match its Birthplace

The natal disk of PDS 70 with new planet PDS 70b (bright spot on the right). Credit: ESO/A. Müller et al.

If the modern age of astronomy could be summarized in a few words, it would probably be “the age of shifting paradigms.” Thanks to next-generation telescopes, instruments, and machine learning, astronomers are conducting deeper investigations into cosmological mysteries, making discoveries, and shattering preconceived notions. This includes how systems of planets form around new stars, which scientists have traditionally explained using the Nebular Hypothesis. This theory states that star systems form from clouds of gas and dust (nebulae) that experience gravitational collapse, creating a new star.

The remaining gas and dust then settle into a protoplanetary disk around the new star, which gradually coalesces to create planets. Naturally, astronomers theorize that the composition of the planets would match that of the disk itself. However, when examining a still-developing exoplanet in a distant star system, a team of astronomers uncovered a mismatch between the gases in the planet’s atmosphere and those within the disk. These findings indicate that the relationship between a protoplanetary disk and the planets they form might be more complicated.

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Webb Observes Protoplanetary Disks that Contradict Models of Planet Formation

Image of the star cluster NGC 346, captured by Webb's Near-Infrared Camera (NIRCam). Credit: NASA, ESA, CSA, STScI, Olivia C. Jones (UK ATC), Guido De Marchi (ESTEC), Margaret Meixner (USRA)

The James Webb Space Telescope (JWST) was specifically intended to address some of the greatest unresolved questions in cosmology. These include all of the major questions scientists have been pondering since the Hubble Space Telescope (HST) took its deepest views of the Universe: the Hubble Tension, how the first stars and galaxies came together, how planetary systems formed, and when the first black holes appeared. In particular, Hubble spotted something very interesting in 2003 when observing a star almost as old as the Universe itself.

Orbiting this ancient star was a massive planet whose very existence contradicted accepted models of planet formation since stars in the early Universe did not have time to produce enough heavy elements for planets to form. Thanks to recent observations by the JWST, an international team of scientists announced that they may have solved this conundrum. By observing stars in the Small Magellanic Cloud (LMC), which lacks large amounts of heavy elements, they found stars with planet-forming disks that are longer-lived than those seen around young stars in our Milky Way galaxy.

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A New Study Suggests How we Could Find Advanced Civilizations that Ran Out of Fusion Fuel

This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. A new study suggests that Earth's water didn't all come from comets, but likely also came from water-rich planetesimals. Credit: NASA
This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. A new study suggests that Earth's water didn't all come from comets, but likely also came from water-rich planetesimals. Credit: NASA

When it comes to our modern society and the many crises we face, there is little doubt that fusion power is the way of the future. The technology not only offers abundant power that could solve the energy crisis, it does so in a clean and sustainable way. At least as long as our supplies of deuterium (H2) and helium-3 hold up. In a recent study, a team of researchers considered how evidence of deuterium-deuterium (DD) fusion could be used as a potential technosignature in the Search for Extraterrestrial Intelligence (SETI).

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Could the ESA’s PLATO Mission Find Earth 2.0?

Artist's impression of the ESA's PLATO mission. Credit: ESA/ATG medialab

Currently, 5,788 exoplanets have been confirmed in 4,326 star systems, while thousands more candidates await confirmation. So far, the vast majority of these planets have been gas giants (3,826) or Super-Earths (1,735), while only 210 have been “Earth-like” – meaning rocky planets similar in size and mass to Earth. What’s more, the majority of these planets have been discovered orbiting within M-type (red dwarf) star systems, while only a few have been found orbiting Sun-like stars. Nevertheless, no Earth-like planets orbiting within a Sun-like star’s habitable zone (HZ) have been discovered so far.

This is largely due to the limitations of existing observatories, which have been unable to resolve Earth-sized planets with longer orbital periods (200 to 500 days). This is where next-generation instruments like the ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission come into play. This mission, scheduled to launch in 2026, will spend four years surveying up to one million stars for signs of planetary transits caused by rocky exoplanets. In a recent study, an international team of scientists considered what PLATO would likely see based on what it would see if observing the Solar System itself.

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MAUVE: An Ultraviolet Astrophysics Probe Mission Concept

An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Could their stars' metallicity play a role in making them habitable to life? Credit: NASA/JPL-Caltech
An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Could their stars' metallicity play a role in making them habitable to life? Credit: NASA/JPL-Caltech

For the past thirty years, NASA’s Great Observatories – the Hubble, Spitzer, Compton, and Chandra space telescopes – have revealed some amazing things about the Universe. In addition to some of the deepest views of the Universe provided by the Hubble Deep Fields campaign, these telescopes have provided insight into the unseen parts of the cosmos – i.e., in the infrared, gamma-ray, and ultraviolet spectrums. With the success of these observatories and the James Webb Space Telescope (JWST), NASA is contemplating future missions that would reveal even more of the “unseen Universe.”

This includes the UltraViolet Explorer (UVEX), a space telescope NASA plans to launch in 2030 as its next Astrophysics Medium-Class Explorer mission. In a recent study, a team comprised of graduate students and postdocs from institutions across the US detailed a concept mission known as the Mission to Analyze the UltraViolet universE (MAUVE). This telescope and its sophisticated instruments were conceived during the inaugural NASA Astrophysics Mission Design School. According to the team’s paper, this mission would hypothetically be ready for launch by 2031.

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New Study Examines How Extraterrestrial Civilizations Could Become “Stellivores.”

Artist's impression of accretion in a binary system. Credit: ESO/L. Calçada

One of the most challenging aspects of astrobiology and the Search for Extraterrestrial Intelligence (SETI) is anticipating what life and extraterrestrial civilizations will look like. Invariably, we have only one example of a planet that supports life (Earth) and one example of a technologically advanced civilization (humanity) upon which to base our theories. As for more advanced civilizations, which statistically seems more likely, scientists are limited to projections of our own development. However, these same projections offer constraints on what SETI researchers should search for and provide hints about our future development.

In a series of papers led by the Blue Marble Space Institute of Science (BMSIS), a team of researchers examines what Earth’s level of technological development (aka. “technosphere”) will look like in the future. In the most recent installment, they offer a reinterpretation of the Kardashev Scale, which suggests that civilizations expand to harness greater levels of energy (planet, host star, and galaxy). Instead, they suggest that the Kardashev Scale establishes upper limits on the amount of stellar energy a civilization can harness (a “luminosity limit”) and that civilizations might circumvent this by harnessing stellar mass directly.

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Project Hyperion is Seeking Ideas for Building Humanity’s First Generation Ship

Project Hyperion is the first design competition for a generation ship. Credit: Maciej Rebisz/Michel Lamontagne

The dream of traversing the depths of space and planting the seed of human civilization on another planet has existed for generations. For long as we’ve known that most stars in the Universe are likely to have their own system of planets, there have been those who advocated that we explore them (and even settle on them). With the dawn of the Space Age, this idea was no longer just the stuff of science fiction and became a matter of scientific study. Unfortunately, the challenges of venturing beyond Earth and reaching another star system are myriad.

When it comes down to it, there are only two ways to send crewed missions to exoplanets. The first is to develop advanced propulsion systems that can achieve relativistic speeds (a fraction of the speed of light). The second involves building spacecraft that can sustain crews for generations – aka. a Generation Ship (or Worldship). On November 1st, 2024, Project Hyperion launched a design competition for crewed interstellar travel via generation ships that would rely on current and near-future technologies. The competition is open to the public and will award a total of $10,000 (USD) for innovative concepts.

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Establishing a New Habitability Metric for Future Astrobiology Surveys

An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Could their stars' metallicity play a role in making them habitable to life? Credit: NASA/JPL-Caltech
An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Could their stars' metallicity play a role in making them habitable to life? Credit: NASA/JPL-Caltech

The search for exoplanets has grown immensely in recent decades thanks to next-generation observatories and instruments. The current census is 5,766 confirmed exoplanets in 4,310 systems, with thousands more awaiting confirmation. With so many planets available for study, exoplanet studies and astrobiology are transitioning from the discovery process to characterization. Essentially, this means that astronomers are reaching the point where they can directly image exoplanets and determine the chemical composition of their atmospheres.

As always, the ultimate goal is to find terrestrial (rocky) exoplanets that are “habitable,” meaning they could support life. However, our notions of habitability have been primarily focused on comparisons to modern-day Earth (i.e., “Earth-like“), which has come to be challenged in recent years. In a recent study, a team of astrobiologists considered how Earth has changed over time, giving rise to different biosignatures. Their findings could inform future exoplanet searches using next-generation telescopes like the Habitable Worlds Observatory (HWO), destined for space by the 2040s.

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Astronomers Solve the Mystery of the Famed Brown Dwarf That is Too Bright: It’s Twins!

This artwork highlights a pair of recently uncovered brown dwarf twins, named Gliese 229 Ba and Gliese 229 Bb. Credit: K. Miller/R. Hurt (Caltech/IPAC)

In 1995, Caltech researchers at the Institute’s Palomar Observatory first observed what appeared to be a brown dwarf orbiting Gliese 229 – a red dwarf star located about 19 light-years from Earth. Since then, this brown dwarf (Gliese 229 B) has mystified astronomers because it appeared too dim for its mass. With 70 times the mass of Jupiter, it should have been brighter than what telescopes had observed. However, a Caltech-led international team of astronomers recently solved the mystery by determining that the brown dwarf is a pair of closely orbiting twins!

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