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Archive 004 · Life004-009

K2-18b

K2-18b is a super Earth or mini Neptune sized planet about 8 to 9 times the mass of Earth, orbiting in the habitable zone of a red dwarf star in Leo. Observations with Hubble and the James Webb Space Telescope have revealed a hydrogen rich atmosphere containing methane, carbon dioxide, and water vapour, leading to debate about whether the planet could host an ocean and even possible chemical signs of life.

The Human Archives artwork

Where the Signal Was Read

Follow the documented locations

01 / Context

Reading a Planet's Air from Far Away

K2-18b was first detected because it passes in front of its host star, causing tiny, regular dips in brightness. When the planet transits, some starlight filters through its atmosphere, imprinting spectral fingerprints that telescopes can measure. Interpreting those spectra requires careful modelling, and small differences in assumptions can change whether a signal looks like water vapour, methane, or something else.

02 / Context

The Risk of Wanting Aliens Too Much

Reports about possible life on K2-18b show how human hopes and caution collide. Some analyses suggest molecules that, on Earth, are made mainly by living things. Other scientists urge restraint, pointing out the noise in the data and the many non-biological ways to produce similar signals. The planet becomes a mirror for our desire to not be alone.

03 / Context

Imagining Other Trees of Life

If life exists on K2-18b, it grew under a red sun, in oceans and atmospheres unlike our own. Stromatolite builders on Earth turned light and water into stone records. On a distant world, some other chemistry might leave different traces for future observers. Thinking about those possibilities sharpens our appreciation of the single biosphere we can study up close.

Artifact Profile

Artifact ID
004-009
Discipline
astronomical
Medium
planet
Collection terms
exoplanet · habitable-zone · jwst · hycean-planet · signs-of-life

About the visual

Visual type
The Human Archives artwork
Authored caption
An artist's impression of a water rich exoplanet with a hazy atmosphere orbiting a cool red dwarf star.

Sources and provenance

  1. NASA K2-18b overview
  2. Carbon bearing molecules in K2-18b's atmosphere
Presentation version
60d0530ccfdfa6b0
Recorded review
2025-01-17

Revision and release records are shown where available. This page does not imply every historical edit has a review record.

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