Life Archives

February 8, 2022February 8, 2022 by Evan Gough

Massive Rocky Planets Probably Don’t Have big Moons

The Earth straddling the limb of the Moon, as seen from above Compton crater on the lunar farside, taken by the Lunar Reconnaissance Orbiter spacecraft. Credit: NASA/GSFC/Arizona State University.

The Moon has orbited Earth since the Solar System’s early days. Anyone who’s ever spent time at the ocean can’t fail to notice the Moon’s effect. The Moon drives the tides even in the world’s most remote inlets and bays. And tides may be vital to life’s emergence.

But if Earth were more massive, the Moon may never have become what it is now. Instead, it would be much smaller. Tides would be much weaker, and life may not have emerged the way it did.

January 11, 2022January 11, 2022 by Evan Gough

Nearby Supernovae Were Essential to Life on Earth

Distant past supernovae could be linked by cosmic ray particles to climate change on Earth and changes in biodiversity. Courtesy: Henrik Svensmark, DTU Space.

It’s almost impossible to comprehend a supernova explosion’s violent, destructive power. An exploding supernova can outshine its host galaxy for a few weeks or even months. That seems almost impossible when considering that a galaxy can contain hundreds of billions of stars. Any planet too close to a supernova would be completely sterilized by all the energy released, its atmosphere would be stripped away, and it may even be shredded into pieces.

But like many things in nature, it all comes down to dose.

A certain amount of supernova activity might be necessary for life to exist.

January 10, 2022January 10, 2022 by Evan Gough

The Early Earth was Really Horrible for Life

The Blue Marble image of Earth from Apollo 17. Credit: NASA

Earth has had a long and complex history since its formation roughly 4.5 billion years ago. Initially, it was a molten ball, but eventually, it cooled and became differentiated. The Moon formed from a collision between Earth and a protoplanet named Theia (probably), the oceans formed, and at some point in time, about 4 billion years ago, simple life appeared.

Those are the broad strokes, and scientists have worked hard to fill in a detailed timeline of Earth’s history. But there are a host of significant and poorly-understood periods in the timeline, lined up like targets for the scientific method. One of them concerns UV radiation and its effects on early life.

A new study probes the effects of UV radiation on Earth’s early life-forms and how it might have shaped our world.

December 14, 2021December 14, 2021 by Evan Gough

Life on Earth Needed Iron. Will it be the Same on Other Worlds?

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

A lot has to go right for a planet to support life. Some of the circumstances that allow life to bloom on any given planet stem from the planet’s initial formation. Here on Earth, circumstances meant Earth’s crust contains about 5% iron by weight.

A new paper looks at how Earth’s iron diminished over time and how that shaped the development of complex life here on Earth. Is iron necessary for complex life to develop on other worlds?

November 24, 2021November 24, 2021 by Evan Gough

Did Cosmic Dust Deliver the Phosphorus Needed for Life?

Sunlight reflects off tiny, interplanetary dust particles, creating the faint column of glowing light seen against the stars in this image. New research suggests that cosmic dust might be an important source of phosphorus for life on Earth. Credit: Malcol, CC BY 3.0

Without phosphorus, there’s no life. It’s a necessary part of DNA, RNA, and other biological molecules like ATP, which helps cells transport energy. But any phosphorus that was present when Earth formed would’ve been sequestered in the center of the molten planet.

So where did phosphorus come from?

It might have come from cosmic dust.

November 22, 2021November 22, 2021 by Evan Gough

Is That a Fossil on Mars? Non-Biological Deposits can Mimic Organic Structures

NASA's Perseverance rover, which is searching signs of ancient life on Mars (credit: NASA/JPL-Caltech/MSSS)

There’s nothing easy about searching for evidence of life on Mars. Not only do we somehow have to land a rover there, which is extraordinarily difficult. But the rover needs the right instruments, and it has to search in the right location. Right now, the Perseverance lander has checked those boxes as it pursues its mission in Jezero Crater.

But there’s another problem: there are structures that look like fossils but aren’t. Many natural chemical processes produce structures that mimic biological ones. How can we tell them apart? How can we prepare for these false positives?

October 12, 2021October 12, 2021 by Evan Gough

Greenland’s Ice Sheet is Similar in Many Ways to the Solar System’s Icy Worlds and Can Teach Us How to Search for Life

Floating ice at the calving front of Greenland's Kangerdlugssuaq glacier, photographed in 2011 during Operation IceBridge (Credit: NASA/Michael Studinger)

Many regions on Earth are temperate, nutrient-rich, stable environments where life seems to thrive effortlessly. But not all of Earth. Some parts, like Greenland’s ice sheet, are inhospitable.

In our nascent search for life elsewhere in the Solar System, it stands to reason that we’ll be looking at worlds that are marginal and inhospitable. Icy worlds like Jupiter’s moon Europa and Saturn’s moon Enceladus are our most likely targets. These frozen worlds have warm oceans under layers of ice.

What can Greenland’s cryo-ecosystems tell us about searching for life on icy bodies like Europa and Enceladus?

October 3, 2021October 3, 2021 by Scott Alan Johnston

When Did Photosynthesis Begin?

Sometime around 2.4 billion years ago, a nascent planet Earth underwent one of the most dramatic changes in its history. Known as the Great Oxidation Event, this period saw Earth’s atmosphere suddenly bloom with (previously scarce) molecular oxygen. The rapid alteration of the atmosphere’s composition was nothing short of a cataclysm for some early lifeforms (at the time, mostly simple celled prokaryotes). Anaerobic species – those that dwell in oxygen-free environments – experienced a near extinction-level event. But the Great Oxidation was also an opportunity for other forms of life to thrive. Oxygen in the atmosphere tempered the planetary greenhouse effect, turning methane into the less potent carbon dioxide, and ushering in a series of ice ages known as the Huronian Glaciation. But oxygen is an energy-rich molecule, and it also bolstered diversity and activity on the planet, as a powerful new source of fuel for living organisms.

The cause of this dramatic event? The tiniest of creatures: little ocean-dwelling cyanobacteria (sometimes known as blue-green algae) that had developed a new super-power never before seen on planet Earth: photosynthesis. This unique ability – to gain energy from sunlight and release oxygen as a waste product – was a revolutionary step for so small a critter. It quite literally changed the world.

October 1, 2021October 1, 2021 by Evan Gough

Rogue Planets Could be Habitable

An artist's illustration of a rogue planet, dark and mysterious. Image Credit: NASA

The search for potentially habitable planets is focused on exoplanets—planets orbiting other stars—for good reason. The only planet we know of with life is Earth and sunlight fuels life here. But some estimates say there are many more rogue planets roaming through space, not bound to or warmed by any star.

Could some of them support life?

September 24, 2021September 24, 2021 by Evan Gough

Galactic Panspermia. How far Could Life Spread Naturally in a Galaxy Like the Milky Way?

A new study expands on the classical theory of panspermia, addressing whether or not life could be distributed on a galactic scale. Credit: NASA

Can life spread throughout a galaxy like the Milky Way without technological intervention? That question is largely unanswered. A new study is taking a swing at that question by using a simulated galaxy that’s similar to the Milky Way. Then they investigated that model to see how organic compounds might move between its star systems.