Habitability Archives

October 17, 2024October 19, 2024 by Matt Williams

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

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.

September 7, 2024September 7, 2024 by Matt Williams

Could Comets have Delivered the Building Blocks of Life to “Ocean Worlds” like Europa, Enceladus, and Titan too?

The "ocean worlds" of the Solar System. Credit: NASA/JPL

Throughout Earth’s history, the planet’s surface has been regularly impacted by comets, meteors, and the occasional large asteroid. While these events were often destructive, sometimes to the point of triggering a mass extinction, they may have also played an important role in the emergence of life on Earth. This is especially true of the Hadean Era (ca. 4.1 to 3.8 billion years ago) and the Late Heavy Bombardment, when Earth and other planets in the inner Solar System were impacted by a disproportionately high number of asteroids and comets.

These impactors are thought to have been how water was delivered to the inner Solar System and possibly the building blocks of life. But what of the many icy bodies in the outer Solar System, the natural satellites that orbit gas giants and have liquid water oceans in their interiors (i.e., Europa, Enceladus, Titan, and others)? According to a recent study led by researchers from Johns Hopkins University, impact events on these “Ocean Worlds” could have significantly contributed to surface and subsurface chemistry that could have led to the emergence of life.

August 6, 2024August 6, 2024 by Matt Williams

Elliptical Orbits Could be Essential to the Habitability of Rocky Planets

Illustration of Kepler-186f, a recently-discovered, possibly Earthlike exoplanet that could be a host to life. (NASA Ames, SETI Institute, JPL-Caltech, T. Pyle) — This is Kepler 186f, an exoplanet in the habitable zone around a red dwarf. We've found many planets in their stars' habitable zones where they could potentially have surface water. But it's a fairly crude understanding of true habitability. Image Credit: NASA Ames, SETI Institute, JPL-Caltech, T. Pyle)

A seismic shift occurred in astronomy during the Scientific Revolution, beginning with 16th-century polymath Copernicus and his proposal that the Earth revolved around the Sun. By the 17th century, famed engineer and astronomer Galileo Galilei refined Copernicus’ heliocentric model using observations made with telescopes he built himself. However, it was not until Kepler’s observations that the planets followed elliptical orbits around the Sun (rather than circular orbits) that astronomical models matched observations of the heavens completely.

As it turns out, this very quirk of orbital mechanics may be essential to the emergence of life on planets like Earth. That was the hypothesis put forth in a recent study by a team of astronomers led by the University of Leeds. According to their work, orbital eccentricity (how much a planet’s orbit deviates from a circle) can influence a planet’s climate response, which could have a profound effect on its potential habitability. These findings could be significant for exoplanet researchers as they continue to search for Earth-like planets that could support life.

July 25, 2024July 25, 2024 by Matt Williams

Planetary Habitability Depends on its Star’s Magnetic Field

Earth's magnetosphere is the region defined by our planet's magnetic field. Image Credit: NASA

The extrasolar planet census recently passed a major milestone, with 5500 confirmed candidates in 4,243 solar systems. With so many exoplanets available for study, astronomers have learned a great deal about the types of planets that exist in our galaxy and have been rethinking several preconceived notions. These include the notion of “habitability” and whether Earth is the standard by which this should be measured – i.e., could there be “super habitable” exoplanets out there? – and the very concept of the circumsolar habitable zone (CHZ).

Traditionally, astronomers have defined habitable zones based on the type of star and the orbital distance where a planet would be warm enough to maintain liquid water on its surface. But in recent years, other factors have been considered, including the presence of planetary magnetic fields and whether they get enough ultraviolet light. In a recent study, a team from Rice University extended the definition of a CHZ to include a star’s magnetic field. Their findings could have significant implications in the search for life on other planets (aka. astrobiology).

June 17, 2024June 17, 2024 by Andy Tomaswick

Which Stars are Lethal to their Planets?

Many years ago, there was a viral YouTube video called “History of the entire world, i guess,” which has been an endless source of internet memes since its release. One of the most prominent is also scientifically accurate—when describing why animals couldn’t start living on land, the video’s creator, Bill Wurtz, intones, “The Sun is a deadly laser.”

March 26, 2024March 26, 2024 by Evan Gough

Europe Has Big Plans for Saturn’s Moon Enceladus

A false-colour image of the plumes erupting from Enceladus. Image Credit: NASA/ESA

Saturn’s moon, Enceladus, is a gleaming beacon that captivates our intellectual curiosity. Its clean, icy surface makes it one of the most reflective objects in the entire Solar System. But it’s what’s below that ice that really gets scientists excited.

Under its icy shell is an ocean of warm, salty water, and the ESA says investigating the moon should be a top priority.

March 26, 2024March 26, 2024 by Evan Gough

Mars’ Gale Crater was Filled with Water for Much Longer Than Anyone Thought

Layers at the base of Mt. Sharp. These visible layers in Gale Crater show the chapters of the geological history of Mars in this image from NASA's Curiosity rover. New evidence from this area shows that water persisted on Mars for longer than thought. Credit: NASA/JPL-Caltech/MSSS.

Even with all we’ve learned about Mars in recent years, it doesn’t stack up against all we still don’t know and all we hope to find out. We know that Mars was once warm and wet, a conclusion that was less certain a couple of decades ago. Now, scientists are working on uncovering the details of Mars’s ancient water.

New research shows that the Gale Crater, the landing spot for NASA’s MSL Curiosity, held water for a longer time than scientists thought.

March 19, 2024March 19, 2024 by Evan Gough

Earth’s Long-Term Habitability Relies on Chemical Cycles. How Can We Better Understand Them?

Biogeochemical cycles move matter around Earth between the atmosphere, the oceans, the lithosphere, and living things. Image Credit: By Alexander Davronov - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=106124364

We, and all other complex life, require stability to evolve. Planetary conditions needed to be benign and long-lived for creatures like us and our multicellular brethren to appear and to persist. On Earth, chemical cycling provides much of the needed stability.

Chemical cycling between the land, atmosphere, lifeforms, and oceans is enormously complex and difficult to study. Typically, researchers try to isolate one cycle and study it. However, new research is examining Earth’s chemical cycling more holistically to try to understand how the planet has stayed in the ‘sweet spot’ for so long.

March 5, 2024March 5, 2024 by Evan Gough

The LIFE Telescope Passed its First Test: It Detected Biosignatures on Earth.

LIFE will have five separate space telescopes that fly in formation and work together to detect biosignatures in exoplanet atmospheres. Image Credit: LIFE, ETH Zurich

We know that there are thousands of exoplanets out there, with many millions more waiting to be discovered. But the vast majority of exoplanets are simply uninhabitable. For the few that may be habitable, we can only determine if they are by examining their atmospheres. LIFE, the Large Interferometer for Exoplanets, can help.

February 26, 2024February 26, 2024 by Evan Gough

If Exoplanets Have Lightning, it’ll Complicate the Search for Life

Lightning on exoplanets could mask some biosignatures and amplify others. Image Credit: NASA/T.Pyle

Discovering exoplanets is almost routine now. We’ve found over 5,500 exoplanets, and the next step is to study their atmospheres and look for biosignatures. The James Webb Space Telescope is leading the way in that effort. But in some exoplanet atmospheres, lightning could make the JWST’s job more difficult by obscuring some potential biosignatures while amplifying others.