Inhabiting Mars without terraforming might be accomplished with 'worldhouses'

The inhabitability of the Martian environment presents significant colonization risks

Terraforming the thin atmosphere, toxic dust, extreme cold, and lack of magnetic field is infeasible, given limitations to the size of what can be sent to Mars. NASA and SpaceX are instead exploring creating underground shelters.

Besides Earth, Mars is the only possibly habitable planet in our solar system

Sending humans to Mars in the following decades poses significant challenges, from the vast distance covered to get materials there to powering technology during weekslong dust storms. Research is ongoing to develop life support systems that can regenerate or recycle consumables.

Why extremophiles may play an important role in terraforming Mars

Possessing unique biochemicals that can detoxify extreme environments and resilience against the Martian surface that is lethal to humans, scientists are exploring whether colonies of these organisms can transform small areas of the Red Planet into future habitats for humans. Extremophiles may also be best equipped to serve as microscopic factories for the fabrication of essential polymers.

Imagining the best places to live on Mars

Because conditions on Mars are pretty extreme for humanity, we tend not to think about living there, since everywhere on Mars feels a bit threatening. This imaginative essay uses current geographical knowledge of Mars to visualize what it would look like if humanity could alter its climate to make it widely habitable, a process known to sci-fi readers as terraforming. Given that transformation, where would the hottest neighborhoods be located?

Biological terraforming studies have been conducted at Biosphere 2

The experiments involve populating barren hillslopes within the Landscape Evolution Observatory with microbes that react with air and rock to produce molecules needed by more complex organisms. Mosses and other simple plants can then grow in these spaces, gradually making them more hospitable to humans.

A prototype greenhouse for Biosphere 2 is now part of a test habitat for Mars

The Space Analog for the Moon and Mars combines the Test Module greenhouse with a workshop, kitchen, common area, sleeping quarters, and a yard that mimics lunar and Martian surfaces. A blind crew member in SAM’s first mission, Inclusion I, helped assess accessibility in potential future space habitats.

Mars once had oceans and a thick atmosphere

It formed over millions of years as small clumps of matter orbiting the sun smashed together, solidified, and cooled. Geological features indicate the presence of past surface water, which evaporated away due to the planet's weak gravitational field.

An artificial ‘lung’ protects the glass structures making up Biosphere 2

Although confined from much of the surrounding environment, B2 allows sunlight to enter, enabling its plants to engage in photosynthesis. Expansion chambers were built to protect the facility's integrity by managing changes in gas pressure resulting from temperature fluctuations.

Mold growth in space raises the hypothesis of life being brought to Earth

Panspermia suggests that life could be carried throughout the cosmos by asteroids, comets, and other objects, but it requires organisms that can withstand the extreme cold of space travel, stellar radiation, lack of water, and intense heat of planetary impacts. The discovery of mold on the International Space Station and experiments showing it can withstand radiation in outer space-like conditions increase the plausibility of the hypothesis.

Martian skies and sunsets resembled Earth's hundreds of millions of years ago

Evidence suggests that Mars has had a thicker atmosphere, which included greenhouse gases, and a magnetic field in its past, resembling Earth's current composition. After losing its magnetic field—the protection from solar wind—the atmosphere and its associated atmospheric phenomena gradually disappeared.

If Earth's water were suddenly replaced with air, forest fires would burn most of the world's vegetation within years.

Solar wind may have contributed to Mars losing its atmosphere

Scientists believe that over hundreds of millions of years, energetic particles from the sun colliding with atmospheric particles, flinging them away from Mars' weak gravitational field like colliding billiard balls. As atmospheric pressure decline, water also evaporated away from the surface.

JWST might spot life faster on ocean worlds than Earth-like ones

Unlike Earth-like planets, hycean worlds with thick hydrogen atmospheres and deep oceans could allow biosignature gases like methyl halides to accumulate in detectable levels. These gases, linked to microbial life on Earth, are easier for the James Webb Space Telescope to identify than traditional markers like oxygen or methane.

Did Mars ever look like Earth?

Mars formed at the same time as the rest of the solar system, about 4.6 billion years ago. Today, Mars is a cold, dry world with a thin atmosphere. However, there is evidence that Mars was once much more habitable, covered in flowing rivers a large bodies of water. Scientists believe over time the planet lost its magnetic field, leading to the loss of atmosphere and ultimately the evaporation of water.

As an experiment, the first B2 mission highlighted the challenges of isolated systems

Some argue that isolation from the outside world was compromised—making the experiment a failure—when a crew member was taken from Biosphere 2 for surgery and returned hours later. This position was strengthened when it was revealed that oxygen had been pumped into the facility.

Why haven’t humans reached Mars?

Mars remains the most viable interplanetary destination due to its relatively habitable orbit. There are many challenges, however, including the huge distance to Mars, the need for advanced propulsion systems, uncertainty over the impacts of long-duration space travel on astronauts, and the need for safe landing techniques and equipment to handle Martian conditions. Human-manned missions to Mars are not likely to occur until the 2030s at the earliest.

Instead of the tectonic plates found on Earth that produce earthquakes, volcanoes, and other geological activity when they interact, Mercury, Mars, and the moon have continuous, unbroken shells of rock called 'stagnant lids.'

Exposed concrete led to oxygen depletion within Biosphere 2

Instead of being absorbed by plants through photosynthesis to produce oxygen, significant amounts of carbon dioxide were taken up by the calcium hydroxide in the concrete, trapping the oxygen in calcium carbonate and water. This concrete was sealed before the start of the second B2 mission.

Some 19th century astronomers thought Mars was inhabited

As telescope technology advanced, astronomers became able to observe the surfaces of objects in our solar system with greater detail. The dips, valleys, and lines crisscrossing Mars, particularly, captured onlookers' imagination, leading some to speculate that the seemingly organized features could only have been created by an intelligent civilization.

Ambient sounds on Mars are lower-pitched and more muted than those on Earth

The planet's thin atmosphere absorbs higher frequencies, and audio captured by the Perseverance rover from the Ingenuity Mars helicopter revealed that sound waves travel farther than previous atmospheric models suggested.

The weight of Earth's atmosphere is equivalent to a 33-foot deep, global ocean

Because air is made up of gas molecules with mass, it is not weightless. On the planet's surface, we are effectively living in what is the equivalent of the bottom of an invisible ocean of these particles pressing against us, just as water molecules do when we are submerged.

Particles found in Martian air pose significant risks to human lungs

Ultrafine dust, just 3 micrometers wide, is small enough to bypass lung defenses and enter the bloodstream, where its highly reactive chemicals can cause thyroid disease. Silica in the dust can also cause silicosis, a chronic and incurable lung disease.

A basement of mechanical systems—collectively called the technosphere—supports B2

Twenty-six underground air handlers heat, cool, filter and manage the humidity of the air across the biomes of Biosphere 2. The above-ground Energy Center complex provides continuous power to these and other systems, including heating and cooling water for laboratory experiments and personal use.

Atmospheric greenhouse gases trap thermal energy and make Earth habitable

The moon and Earth are at the same distance from the sun, but the moon experiences large fluctuations in surface temperature because it lacks an atmosphere to insulate it. Gases such as water vapor, ozone, carbon dioxide, and methane can intercept about 90% of the infrared radiation emitted by Earth's surface.

If the sun disappeared, we would not know about it for 8 minutes and 20 seconds, at which point the Earth would suddenly move in a straight line on its way out of the solar system.

Viking established entry, descent, and landing methods for future planetary visits

The most significant engineering challenge was slowing the Viking lander, which would move through space at nearly 29,000 kilometers per hour before reaching Mars. This required the invention of supersonic parachute technology, which is still used today.

Geological features on Mars' surface provide evidence of massive past flooding

The presence of river valleys, enormous canyons, and other structures carved by water on Earth suggests that water flowed abundantly across Mars' surface. The layering of rocks in the walls of these structures indicates the intensity and volume of these flows.

Biosphere 2 is the largest Earth science experiment ever built

The vivarium—an enclosed system including animals and plants—is sealed from below with 454 metric tons of stainless steel liner and includes an ocean habitat with more than 700,000 gallons of seawater. B2 is visited by 100,000 people yearly, including more than 10,000 K-12 students.

Early Earth lifeforms likely made energy via mineral reactions, not sunlight

Earth's initial atmosphere was filled with carbon dioxide, methane, and water, with most oxygen locked away in the rocky crust. Over time, bacteria evolved to slowly release that oxygen into the atmosphere by breaking down rock.

Exoplanet atmospheric gas patterns may indirectly provide evidence for life

When searching for life beyond the solar system, scientists first determine the range of distances from a star that liquid water—believed to be essential for life—can be found. Within this habitable zone, the presence of specific molecules in an exoplanet's atmosphere—detectable through spectral analysis—can indicate the presence of living things known to produce those compounds.

Understanding why suction cups rely on Earth's atmosphere to work

When pressed against a surface, air is squeezed out of a sealed volume, causing the internal pressure to drop below the surrounding atmospheric pressure, and this imbalance creates the "sticking." For this reason, astronauts do not use suction cups or related technologies to stay on spacecraft during spacewalks.

How the loss of Earth's atmosphere would cause oceans to boil at freezing temperatures

Many phenomena requiring air pressure, from the flight of birds and aircraft to the act of breathing, would no longer be possible. Because sound travels through vibrating air molecules, the loss of the planet's atmosphere would also create a silent environment. Even during daytime hours, the sky would resemble a clear night sky.

The history of Earth's breathable atmosphere, made possible by photosynthetic bacteria

Between 3.2 billion and 2.8 billion years ago, threadlike microorganisms called cyanobacteria began consuming available water vapor, carbon dioxide, and sunlight to produce oxygen. However, molecules released from Earth's interior by volcanoes consumed this oxygen via chemical reactions, preventing it from accumulating until volcanism had sufficiently decreased about 2.4 billion years ago.

Tidally locked exoplanets experience extreme atmospheric temperatures

On worlds like WASP 76b, which orbits its host star approximately 3% the Earth-sun distance, temperatures on its day side can vaporize iron. Winds more than 14 times the speed of sound blow this material to its night side, where it condenses and falls as liquid metal.

Research shows Venus would be hotter if some of its CO₂ were swapped out

The planet's atmosphere—whose density is 92 times that of Earth's—is 96.5% carbon dioxide. Since these molecules all capture the same subset of infrared radiation emitted from Venus's surface, radiation outside this range escapes, demonstrating the increased impact that diverse greenhouse gas composition has on planetary warming.

A four-billion-year-old meteorite reignited the debate about life on Mars

Recovered from Antarctica in 1984, ALH84001 contained organic compounds, magnetite and iron sulfide grains of potential biological origin, and features that resembled fossilized bacteria. With technological advancements, scientists found abiotic origins for these features in the following decades.

The fortunate factors that make life on Earth possible

The Earth is teeming with life while all the other exoplanets and planets aren't. A very specific set of aligned factors forms the habitability of our planet, and without just one of these fortunate factors, we might not be here. This piece lists...

How NASA plans to build a lunar base, from roads to habitats

The Apollo program aspires to return humans to the moon—and to build humanity's first permanent habitat on its surface. The project involves complex construction plans, including creating roads from moon dust, baking bricks to build habitats, and more.

Lining up every microbe on Earth would stretch to about 105,000 light-years

There are about 10²⁷ such organisms on the planet, many of which are adapted to produce energy through uncommon reactions in unconventional environments, such as within rocks or near volcanoes on the ocean floor. Studies of these organisms have reframed astrobiologists' search for life beyond Earth by broadening the parameters under which life can exist.

NASA's ESCAPADE mission will study Mars' atmosphere

The $80M mission—a collaboration between private companies, universities, and NASA—sent two copy machine-sized orbiters on a Blue Origin rocket to the red planet to study its magnetic field and atmospheric loss.

Without greenhouse gases, Earth's average surface temperature would be below freezing

Atmospheric molecules that absorb and emit infrared radiation from the planet's surface effectively trap additional incident solar energy that would otherwise escape to space. Without the greenhouse effect, the planet's average surface temperature would be approximately -18 degrees Celsius (0 degrees Fahrenheit).

Mars' orbit may provide evidence that dark matter is made of primordial black holes

Physicists at MIT have found that, statistically, one such microscopic black hole should pass through the solar system every decade, which they predict would introduce a detectable wobble in Mars' orbit. Such black holes would have formed in the early universe from collapsing gas clouds and scattered as the universe expanded.

Tardigrades have not been shown to survive all space conditions at once

A 2007 mission launched several species into low-Earth orbit, exposing them to microgravity in temperature-controlled modules. Survivability rates were high for microgravity exposure alone, but plummeted when combined with exposure to the full UV spectrum and the vacuum of space.

Mars features distinct geographic contrasts between its northern and southern regions

Unlike the uniform terrains found in most rocky planets, Mars has a smooth, low northern hemisphere and a rough, high southern hemisphere with much thicker crust. This dichotomy may originate from a massive collision early in the planet’s history.

Extremophiles were likely to have been Earth's first, and are expected to be its last, organisms

Their ability to survive in an enormous range of environmental conditions, including some resembling what has been modeled to have existed relatively shortly after Earth's formation, makes them the leading candidates for enduring the increasing solar intensity and the subsequent effects (e.g., zero-oxygen atmosphere, evaporated oceans) expected in the coming billions of years.

Watch a documentary on what the first 10,000 days of colonizing the moon look like

Alongside the construction of the first lunar base with help from SpaceX's Starship Human Landing System, transported astronauts would establish a sustainable human presence through the construction of lunar dust shields, light-bending towers, and 3D-printed habitats.

Excluding water vapor, greenhouse gases make up less than 1% of Earth's atmosphere

Although carbon dioxide, methane, nitrous oxide, ozone, and most fluorinated gases account for only a minority of the planet's greenhouse effect due to their lower concentrations, they are more effective at trapping thermal radiation. While water vapor condenses within two weeks, other greenhouse gases linger in the atmosphere for years on average.

Learn how to build your own vivarium

Creating a self-contained habitat for plants and microscopic animals requires a careful balance of organisms that maintain a cycle of water, nutrients, and other chemicals throughout. Bottlenecks in these cycles are mitigated through careful construction, such as incorporating a drainage layer to effectively manage water.

Why Earth will be made uninhabitable by the sun far sooner than when the sun dies

The star has enough fuel to continue fusing hydrogen into helium for another 5 billion years, but the gradual increase in core temperature from these reactions will brighten the sun by 10% every billion years. Some models predict that the increased radiation will be enough to vaporize all of Earth's surface water about 1 billion years from now, long before the sun becomes a red giant and disintegrates the planet.

Astronauts on the International Space Station have tested an algae-powered bioreactor that converts carbon dioxide, water, and light into oxygen and edible, protein-rich biomass.