Is Mars Really Red? Only From Far Enough Away

Point a camera at the ground directly under a Mars rover and the picture that comes back is not red. NASA’s own summary of the surface lists the colours as brown, gold and tan. From an orbiter the ground reads closer to butterscotch. The colour behind the nickname only assembles itself at a distance, out of dust hanging in the air.

Rust is doing the colouring. The mineral responsible forms in water, and Mars today is what the researchers who identified it call a hyper-arid environment, which makes the planet’s colour a leftover rather than a current event.

Is Mars really red?

Mars is red from a distance and a different colour up close. Iron minerals in the Martian dirt have oxidised, or rusted, and windblown dust carries that rusted material across the entire planet, which is what an observer on Earth sees. On the ground, NASA describes the surface colours as brown, gold and tan.

Both halves of that come from the same place. NASA’s Mars facts page says “iron minerals in the Martian dirt oxidize, or rust, causing the surface to look red” and that “This dust gets kicked up into the atmosphere and from a distance makes the planet appear mostly red”. The same page states it flatly: “The Red Planet is actually many colors.”

Up close the ground is butterscotch

NASA’s Jet Propulsion Laboratory runs a short explainer series called Mars in a Minute, and one episode carries this exact question as its title. The answer JPL gives is that a close-up view from an orbiter, lander or rover shows “a lot of Mars is actually more of a butterscotch color”, and that “Depending on what minerals are around, some landscapes can be more golden, brown, tan, or even a little greenish”.

The dust in the air changes the sky rather than the ground. Rusty dust lofted into the atmosphere, in JPL’s words, “makes the martian sky look pink”.

Where you are looking from	Colour NASA reports
Earth, naked eye	”a reddish tint”
The martian sky, dust aloft	”pink”
Orbiter, lander or rover, close up	”more of a butterscotch color”
The ground, mineral by mineral	”golden, brown, tan, or even a little greenish”

The Red Planet is not red all the way down

The picture of Mars as red throughout, the way a brick is red throughout, is folklore rather than a measurement. What gets measured is a colour at the top: oxidised minerals and dust on and near the surface, with the rock beneath taking its colour from whatever minerals it contains. NASA’s own list of surface colours is brown, gold and tan.

Curiosity supplied a direct look in February 2013. In NASA’s caption for the first powdered rock the rover drilled out, the sample from a slab called John Klein is “gray-green” in the white-balanced version, sitting in a scoop that still carried “red residue” from an earlier sample of windblown dust and sand.

Popular explanations often get assembled backwards from one striking image, as they did for cats and cucumbers. A planet that shows up red in every telescope photograph invites the assumption that it must be red all the way in.

The air on Mars did not do the rusting

The everyday image of rust involves damp air and ordinary oxygen. Mars offers almost none of either. NASA lists the thin Martian atmosphere as “made up mostly of carbon dioxide, nitrogen, and argon gases”, and oxygen does not appear on that list.

How little there is to breathe was demonstrated by an instrument built to fix the problem. NASA’s MOXIE experiment rode to Mars aboard the Perseverance rover and made oxygen electrochemically, stripping one oxygen atom off each carbon dioxide molecule pumped in from the atmosphere. Across 16 runs it produced 122 grams of oxygen in total, peaking at 12 grams an hour at 98 percent purity or better.

Iron oxide is the pigment doing the colouring in both places, which is also why barns on Earth ended up that shade before anyone was selling paint ready-mixed in a tin.

The pigment has water in its formula

In February 2025 a team led by Adomas Valantinas published a paper in Nature Communications called Detection of ferrihydrite in Martian red dust records ancient cold and wet conditions on Mars. The finding is that the dominant iron oxide-bearing phase in Martian dust is ferrihydrite, formula Fe5O8H nH2O. The authors set that against the older reading in the second line of their abstract: “Previous studies attributed Mars’ red color to anhydrous hematite formed through recent weathering.”

The nH2O on the end is not decoration. Ferrihydrite is a hydrated iron oxide, and the paper describes it forming on Earth “through rapid Fe2+ oxidation in aqueous environments at circumneutral pH and low temperatures”. Liquid water, and cold water at that.

That the mineral survives at all, the team writes, suggests it “formed during a cold, wet period on early Mars under oxidative conditions, followed by a transition to the current hyper-arid environment”. Conditions like that, the paper adds, could have existed in the late Hesperian, approximately 3 billion years ago.

Ferrihydrite is a hydrated iron oxide, which puts water into the chemical formula of the pigment itself. On that reading the planet’s most familiar feature is a residue of surface water, left behind in a cold, wet spell the paper places around 3 billion years ago.

The dust does the painting

Martian dust is very fine. A 2025 iScience paper on Martian dust simulant cites the commonly accepted value for the effective radius of Martian dust as approximately 1.5 micrometres.

Particles that small travel. NASA notes that winds on Mars are occasionally strong enough to create dust storms that cover much of the planet, and the ferrihydrite team describes Martian dust as “well mixed on a global scale”. One pigment, stirred everywhere, is why ground that is golden in one place and greenish in another still reads as a single colour from Earth. Path length works the other way for water: a glass of it looks clear, and the ocean’s blue builds up only over metres, as each one absorbs more red light than blue.

Ordinary signals carry more information than they look like they carry, which is also true of the noise a field makes after dark.

Mars answers to its nickname because of what dust does to light on the way out. Land on it and the performance stops: brown, gold, tan, an occasional greenish tint, and a fine rusty powder over the top that is chemically a leftover from a wetter, colder world. The Red Planet is a name earned at a distance, and it does not survive the trip. Strictly FYI.