TRAPPIST-1 SYSTEM / PLANETARY DOSSIER

TRAPPIST-1 c

A slightly larger-than-Earth planet whose infrared light tests the limits of possible atmospheres.

Planetary view ↗

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Artist’s impression of TRAPPIST-1 c; appearance is hypothetical; diameter is inferred from transits
Earth-sized rocky exoplanet

A rocky neighbor with a different kind of heat.

Environment ↗

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ATMOSPHERE

No thick CO₂ blanket

DIAMETER
1.097 × Earth
POSSIBILITY FOR LIFE
Unknown · inner orbital region
WITHOUT PROTECTION
Not established as survivable

Orbit ↗

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≈ 2.42 Earth days

One year around TRAPPIST-1

0.0158 AU · semimajor axisSchematic · not to scale
Sources ↗

Mass comparison ↗

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DYNAMICAL MASS1.308 × Earth

± 0.056 Earth masses

Mutual gravitational perturbations shift transit times, constraining planetary masses.

Landscape ↗

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An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.
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TRAPPIST-1 C

Instrument detail

Artist’s impression of TRAPPIST-1 c

Artist’s impression · appearance is hypothetical; diameter is inferred from transits.

A year in the seven-world chain.

Planet c follows b in the compact inner system. Its orbit takes roughly two and a half Earth days, yet it receives less starlight than b because it is farther from the same faint host. Comparing neighbors helps separate the effects of stellar heating from differences in their own composition and history.

A silhouette we can measure.

Its measured radius is close to b’s and modestly greater than Earth’s. Similar sizes do not guarantee similar skies. Two rocky planets can diverge through atmospheric escape, volcanic history or volatile inventory. The ochre palette gives c an identity in the atlas without assigning it a measured surface chemistry.

What the light can tell us.

Webb’s infrared observations rule out a thick Venus-like carbon-dioxide atmosphere. A much thinner atmosphere remains a different possibility; no breathable air is established. The linked result describes observational limits, while the three scenes illustrate one possible setting.

An imagined place beyond the measurements.

Basins, cliffs and ridges provide three distinct viewpoints on a possible rocky world. No particular crater or mineral has been resolved. The illustrations deliberately leave out buildings and biological features. A compelling view is useful for exploration, but it does not fill the gaps in atmospheric or habitability evidence.

Size, mass and atmosphere

DIAMETER / EARTH1.097 ×

+0.014 / −0.012 · Earth-relative ratio

Agol et al. (2021), Table 6. Radius inferred from transit depth and stellar size. Radius and diameter have the same Earth-relative ratio; this does not resolve terrain.

DYNAMICAL MASS / EARTH
  • TRAPPIST-1 c1.308 ± 0.056 M⊕
  • Earth · reference mass1.00 M⊕

Shared scale: 0–1.5 Earth masses. Mutual gravitational perturbations shift transit times, constraining planetary masses. Agol et al. (2021), Table 6. Dynamical mass from transit-timing variations with an adopted stellar mass; not a radial-velocity minimum.

ATMOSPHERE / COMPOSITION

No thick CO₂ blanket

Webb’s infrared observations rule out a thick Venus-like carbon-dioxide atmosphere. A much thinner atmosphere remains a different possibility; no breathable air is established.

Habitability

NATURAL CONDITIONSUnknown · inner orbital region

No life or surface liquid water has been detected. Stellar heating is only one condition for a possible habitat; atmospheric retention, composition and climate also matter.

HUMANS / WITHOUT PROTECTIONNot established as survivable

Breathable air, safe pressure and tolerable temperatures are not known. A survival time would be speculation.

SURFACE TEMPERATURE
Not a measured global climate
SURFACE PRESSURE
Unknown
STELLAR IRRADIATION
≈ 2.214 × Earth
SURFACE GRAVITY
≈ 1.086 × Earth · mass/radius inference

A year around TRAPPIST-1

≈ 2.42 Earth days

Semimajor axis: 0.0158 AU. One astronomical unit is approximately the mean Earth–Sun distance.

The overview is a schematic: sizes, orbital shape and the planet’s position are illustrative. It does not show a measured eccentricity, the orbit’s orientation or a live position.

Planet c follows b in the compact inner system. Its orbit takes roughly two and a half Earth days, yet it receives less starlight than b because it is farther from the same faint host. Comparing neighbors helps separate the effects of stellar heating from differences in their own composition and history.

Agol et al. (2021) · orbital measurements ↗
An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

Above the ochre basin

An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

Between the pale blocks

An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

The cratered horizon

An imagined view of pale ochre rock, sharp crater terraces and angular blocks. The terrain and mineral colors are invented. An airless sky is an illustration assumption, not a measured atmospheric state. No landing site has been mapped here.

Planet and landscape images are hypothetical artistic interpretations.