Parts of the Atacama Desert have never seen a drop of rain

Introduction: the driest place on the planet isn't a pole

A desert that breaks every record for aridity

When people think of the driest places on Earth, they naturally picture the Sahara or the polar regions. Yet the title of the driest non-polar place on the planet belongs to the Atacama Desert, a strip of land wedged between the Andes mountain range and the Pacific Ocean, in northern Chile. Some weather stations there have recorded, since measurements began, an almost total absence of measurable rainfall, a phenomenon so extreme it has fascinated climatologists for decades. Even seasoned desert researchers admit they had to double-check their instruments the first time they saw readings this low.

This is not journalistic exaggeration: several areas at the heart of the Atacama can go years, even decades, without any significant rainfall. This hyperarid climate results from a rare combination of geographic and oceanic factors that turn this region into a genuine open-air natural laboratory for scientists around the world. Few places on Earth combine so many extreme variables in a single, accessible location.

Why this region fascinates scientists so much

What makes the Atacama particularly interesting isn't just its record-breaking aridity, but everything it allows researchers to study. Space agencies, first and foremost NASA, consider certain portions of this desert to be the closest terrestrial analogue to conditions on the surface of Mars. The ground there is so dry, so poor in detectable organic matter, and so exposed to ultraviolet radiation that it reproduces, fairly faithfully, the extreme environment of the red planet. Visiting researchers often describe the sensation of walking across certain Atacama plains as the closest thing to setting foot on Mars without leaving Earth.

This resemblance has led research teams to multiply their field missions in the Atacama to test instruments, life-detection methods, and scientific protocols that will later be used during future Mars missions. The Chilean desert has thus become, almost by accident, a genuine full-scale training ground for space exploration. Engineers now schedule regular expeditions there years in advance of planned missions.

Why it almost never rains in parts of the Atacama

The decisive role of cold ocean currents

The explanation for this extreme dryness starts with an oceanographic phenomenon well known to specialists: the Humboldt Current. This ocean current, which carries cold water up from Antarctica along the South American Pacific coast, cools the air above the ocean adjacent to the desert. Cold air holds far less moisture than warm air, which considerably limits the formation of rain-bearing clouds above the coastal region.

This cooling also creates a persistent thermal inversion, an atmospheric phenomenon that traps cold, moist air near the surface while preventing the vertical convection needed to form storms and typical rainfall. The result: even when moisture is present as coastal fog, locally called camanchaca, it almost never turns into actual rain. Locals have learned to harvest this fog directly for drinking water, using simple mesh nets strung between poles.

The barrier effect of the Andes mountain range

The second key factor behind this extreme aridity is purely geographic. The Andes mountain range, which borders the Atacama to the east, acts as a natural wall blocking humid air masses arriving from the Amazon and the Atlantic. This effect, known as a rain shadow, deprives the desert of any moisture source coming from the continent, on top of what is already blocked on the ocean side by the Humboldt Current.

Squeezed between these two climatic barriers, the Atacama ends up doubly deprived of rainfall, which explains why some weather stations located in its most remote areas can show, over periods spanning several decades, a cumulative measurable rainfall close to zero. Some of these stations have gone entire operational lifetimes without ever registering a single rain event worth recording.

The microscopic life that survives against the odds

Unexpected extremophile microorganisms

One might assume that soil this dry and this exposed to ultraviolet rays would be completely sterile, devoid of any form of life. Research conducted on site over several years reveals exactly the opposite. Teams of microbiologists have identified, in the most arid soils of the Atacama, communities of extremophile microorganisms capable of surviving in conditions once thought incompatible with any detectable biological activity. Their discovery forced a rethink of what scientists previously considered the outer limits of habitability on Earth.

These organisms, often bacteria or microscopic fungi adapted to extremely low humidity levels, manage to exploit the rare occasions when coastal fog or an exceptional rainfall delivers a minimum amount of water. Some of them enter states of prolonged dormancy, somewhat like dormant spores, waiting for favorable conditions that may only occur once a decade. This kind of extreme patience has no real equivalent among more familiar terrestrial organisms.

What these organisms teach us about the possibility of life elsewhere

The discovery of these microscopic life forms in one of the most hostile environments on our planet has implications that go far beyond the scope of terrestrial biology. For astrobiologists, every new extremophile species identified in the Atacama represents an additional clue suggesting that life, at least in microbial form, could potentially persist in equally arid and hostile Martian environments.

It is precisely this logic that drives NASA and other space agencies to fund sample-collection campaigns in the Chilean desert, using sterilization protocols and handling procedures modeled on those that would be used during a Mars sample-return mission. The Atacama thus becomes a methodological training ground as much as an object of study in its own right. Engineers rehearse entire sampling sequences there long before any hardware ever leaves Earth.

The Atacama as an open-air Martian laboratory

Instruments tested before their launch into space

Beyond simple observation, the Atacama serves as a concrete testing ground for scientific equipment destined for space exploration. Prototype rovers, miniature drills, and biological detection sensors have been deployed there under conditions deliberately similar to those an instrument would encounter on the Martian surface. These trials help identify an instrument's technical weaknesses before it is integrated into a space mission costing several hundred million dollars. A flaw caught here, on Earth, is infinitely cheaper to fix than one discovered millions of kilometers away.

This pragmatic approach shows how space research, often perceived as distant and abstract, is actually grounded in very concrete terrestrial experiments, carried out in landscapes that have nothing to envy, visually, in certain photographs sent back by rovers currently operating on the red planet.

A region also studied for its own climate issues

Scientific interest in the Atacama isn't limited to its role as a Mars analogue. Climatologists also study the dynamics of the Humboldt Current and the coastal thermal inversion there, mechanisms that influence not only the local climate but also, more broadly, rainfall patterns along the entire South American Pacific coastline, with repercussions for agriculture and water availability for local populations. Mining operations in the region, in particular, depend heavily on understanding these long-term water patterns.

This dual scientific role, both terrestrial and space-related, explains why the Atacama continues to attract significant research funding and international collaborations between space agencies, universities, and meteorological institutes, all eager to unlock the last mysteries of this extraordinary desert.

Decades of drought records

Weather stations that barely register anything

Readings taken by various weather stations installed in the most remote parts of the Atacama produce numbers that seem almost unreal to anyone living in a temperate or tropical climate. Some of these stations show average annual rainfall totals of less than one millimeter, a level so low it sits practically at the edge of what measuring instruments can reliably detect.

Over monitoring periods spanning several decades, some sites have simply recorded no measurable rain event at all, making them unique case studies for climatologists seeking to understand the extreme limits of continental aridity. This data feeds scientific databases consulted well beyond Chile's borders, notably by North American and European research teams.

A mineral landscape shaped by millions of years of drought

This near-total absence of rainfall over such a long period has also shaped a distinctive geological landscape, marked by salt formations, natural nitrate deposits, and soils lacking the vegetation cover found in most other deserts on the globe. Some geologists even estimate that certain portions of Atacama soil may not have seen significant rain in millions of years, a climatic age that far exceeds the human timescale.

This extreme geological stability, combined with the absence of water erosion, allows researchers to find mineral structures and chemical traces remarkably well preserved, offering a unique window into geological processes that, elsewhere on Earth, would have long since been erased by the action of water.

What to take away from this extraordinary desert

A climatic extreme that remains rare on Earth

In short, certain areas of the Atacama rank among the rare places on the planet where the absence of measurable rainfall is counted in decades rather than months, a climatic extreme made possible by the combination of the Humboldt Current and the barrier effect created by the Andes mountain range. This unique case shows just how much geography and oceanography can, together, shape environments with almost extraterrestrial characteristics.

Far from being a simple sterile desert, this region is home to extremophile microorganisms whose study directly feeds thinking about the possibility of life elsewhere in the solar system, while also serving as a full-scale testing ground for tomorrow's space exploration technologies.

A lesson in humility in the face of Earth's extremes

This story reminds us that our own planet still holds extreme environments that can shed light on our understanding of other worlds, without needing to leave Earth's atmosphere at all. The Atacama remains a constant reminder that the line between terrestrial exploration and space exploration is sometimes thinner than we imagine.

The next time you hear about a future Mars mission, there is a good chance that some of the scientific equipment or protocols used were already tested, years earlier, in this Chilean desert, as arid as it is fascinating, under one of the clearest and most closely studied skies on the entire planet.

By Maxime Marquette, columnist

Sources

Primary sources

Jet Propulsion Laboratory, research on terrestrial analogues of Mars — 2026

NASA Science, climate and astrobiology studies — 2026

National Oceanic and Atmospheric Administration, data on the Humboldt Current — 2026

Secondary sources

National Geographic France, environment — 2026

Futura Sciences, planet section — 2026

Sciences et Avenir — 2026