Habitability Archives

January 18, 2023January 18, 2023 by Evan Gough

Could Next-Generation Telescopes See That Earth Has Life?

In this image, Earthshine lights up the dark portion of the lunar surface. Image Credit: NASA

While the Earth absorbs a lot of energy from the Sun, a lot of it is reflected back into space. The sunlight reflected from Earth is called Earthshine. We can see it on the dark portion of the Moon during a crescent Moon. The Farmer’s Almanac said it used to be called “the new Moon in the old Moon’s arms.”

Earthshine is one instance of planetshine, and when we look at the light from distant exoplanets, we’re looking directly at their planetshine without it bouncing off another object.

If distant astronomers were looking at Earthshine the way we look at exoplanet shine, would the light tell them our planet is rippling with life?

December 20, 2022December 20, 2022 by Evan Gough

We Could Spread Life to the Milky Way With Comets. But Should We?

Gerald Rhemann captured this incredible image of Comet Leonard when a piece of the comet's tail was disconnected and carried away. Rhemann won Astronomy Photographer of the Year 2022 for the image. Image Credit: Gerald Rhemann

Here’s a thorny problem: What if life doesn’t always appear on planets that can support it? What if we find more and more exoplanets and determine that some of them are habitable? What if we also determine that life hasn’t appeared on them yet?

Could we send life-bringing comets to those planets and seed them with terrestrial life? And if we could do that, should we?

December 14, 2022December 14, 2022 by Evan Gough

Could Life Survive on Frigid Exo-Earths? Maybe Under Ice Sheets

This artist's illustration shows what an icy exo-Earth might look like. A new study says liquid water could persist under ice sheets on planets outside of their habitable zones. Image Credit: NASA

Our understanding of habitability relies entirely on the availability of liquid water. All life on Earth needs it, and there’s every indication that life elsewhere needs it, too.

Can planets with frozen surfaces somehow have enough water to sustain life?

November 24, 2022November 24, 2022 by Evan Gough

What’s the Best Mix of Oceans to Land for a Habitable Planet?

A new study asks what ratio of land to ocean is best for habitability? Image Credit: Reto Stöckli, Render by Robert Simmon. Based on data from the MODIS Science Team

Earth is about 29% land and 71% oceans. How significant is that mix for habitability? What does it tell us about exoplanet habitability?

October 20, 2022October 20, 2022 by Nancy Atkinson

Curiosity Arrives in a Salty Region of Mars. Was it Left Over From a Dying Sea?

A Mastcam image from the Mars Science Laboratory Curiosity rover on Sol 3609 of its mission. Credit: NASA/JPL-Caltech/MSSS/Kevin M. Gill.

The Curiosity rover has now reached its primary target on Mount Sharp on Mars, the mountain in the middle of Gale Crater the rover has been climbing since 2014. This target is not the summit, but a region over 600 meters (2,000 feet) up the mountain that planetary geologists have long anticipated reaching.

Known as the “sulfate-bearing unit,” the region is a boundary between the rocks that saw a lot of water in their history and those that didn’t; a possible shoreline, if you will. That boundary is already providing insights into Mars’ transition from a wet planet to dry, filling in a key gap in the understanding of the planet’s history.

October 14, 2022October 16, 2022 by Evan Gough

If Earth Were an Exoplanet, it Would Still be Tricky to Figure Out if There’s Life Here

Earth as seen by the JUNO spacecraft in 2013. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill.

How would Earth appear to alien astronomers? What would their observations tell them about Earth if they searched the heavens for signs of habitability like we are? It’s a fun thought experiment.

But the experiment is more than just fun: it’s scientifically instructive. In many ways, it’s easier to study our planet and how it appears and then extrapolate those results as far as they go.

A new study shows that finding evidence of life on Earth may depend on the season alien astronomers are observing.

May 11, 2022May 11, 2022 by Evan Gough

These are the Best Places to Search for Habitable Exomoons

An artist's conception of a potentially-habitable exomoon. Credit: NASA

Our Solar System contains eight planets and more than 200 moons. The large majority of those moons have no chance of being habitable, but some of them—Europa and Enceladus, for example—are strong candidates in the search for life.

Is it the same in other solar systems?

February 15, 2022 by Evan Gough

Planet Found in the Habitable Zone of a White Dwarf

An artist’s impression of the white dwarf star WD1054–226 orbited by clouds of planetary debris and a major planet in the habitable zone. Credit Mark A. Garlick / markgarlick.com Licence type Attribution (CC BY 4.0)

Most stars will end their lives as white dwarfs. White dwarfs are the remnant cores of once-luminous stars like our Sun, but they’ve left their lives of fusion behind and no longer generate heat. They’re destined to glow with only their residual energy for billions of years before they eventually fade to black.

Could life eke out an existence on a planet huddled up to one of these fading spectres?

February 11, 2022February 11, 2022 by Evan Gough

We Might Know Why Mars Lost its Magnetic Field

This figure shows a cross-section of the planet Mars revealing an inner, high density core buried deep within the interior. Dipole magnetic field lines are drawn in blue, showing the global scale magnetic field that one associates with dynamo generation in the core. Mars must have one day had such a field, but today it is not evident. Perhaps the energy source that powered the early dynamo has shut down. The differentiation of the planet interior - heavy elements like iron sinking towards the center of the planet - can provide energy as can the formation of a solid core from the liquid. Credit: NASA/JPL/GSFC

Mars is a parched planet ruled by global dust storms. It’s also a frigid world, where night-time winter temperatures fall to -140 C (-220 F) at the poles. But it wasn’t always a dry, barren, freezing, inhospitable wasteland. It used to be a warm, wet, almost inviting place, where liquid water flowed across the surface, filling up lakes, carving channels, and leaving sediment deltas.

But then it lost its magnetic field, and without the protection it provided, the Sun stripped away the planet’s atmosphere. Without its atmosphere, the water went next. Now Mars is the Mars we’ve always known: A place that only robotic rovers find hospitable.

How exactly did it lose its magnetic shield? Scientists have puzzled over that for a long time.

December 31, 2021December 31, 2021 by Matt Williams

An Exoplanet Found Protected by a Magnetosphere

Today’s astronomers are busy building the census of extrasolar planets, which has reached a total of 4,884 confirmed planets, with another 8,288 candidates awaiting confirmation. Now that the James Webb Space Telescope (JWST) has finally been launched, future surveys will be reaching beyond mere discovery and will be focused more on characterization. In essence, future exoplanet surveys will determine with greater certainty which planets are habitable and which are not.

One characteristic that they will be on the lookout for in particular is the presence of planetary magnetic fields (aka. magnetospheres). On Earth, the atmosphere and all life on the surface are protected by a magnetic field, which is why they are considered crucial to habitability. Using data from the venerated Hubble Space Telescope (HST), an international team of astronomers reported the detection of a magnetic field around an exoplanet for the first time!