---
type: claim
domain: space-development
description: "C-type asteroids (75% of known asteroids) carry 10-20% water ice plus carbon compounds and organics; OSIRIS-REx Bennu sample confirmed amino acids, nucleobases, and minerals unseen on Earth"
confidence: likely
source: "Astra, web research compilation February 2026; OSIRIS-REx Bennu sample analysis 2025"
created: 2026-02-17
secondary_domains:
  - manufacturing
depends_on:
  - "asteroid mining economics split into three distinct business models with water-for-propellant viable near-term and metals-for-Earth-return decades away"
  - "water is the strategic keystone resource of the cislunar economy because it simultaneously serves as propellant life support radiation shielding and thermal management"
sourced_from:
- inbox/archive/2026-02-17-astra-space-asteroid-mining.md
---

# C-type carbonaceous asteroids containing 10-20 percent water by mass are the near-term mining targets because water closes first economically

Asteroids divide into three spectral types with distinct resource profiles. C-type (carbonaceous) asteroids -- comprising 75% of known asteroids -- are rich in water ice (10-20% by mass), carbon compounds, organic molecules, and clays. S-type (silicaceous, 17%) contain nickel, iron, magnesium, and silicate minerals with moderate platinum group metal concentrations, often in free unoxidized state. M-type (metallic, 8%) hold the highest concentrations of iron, nickel, cobalt, and platinum group metals, with platinum grades up to 100 grams per ton versus 3-5 g/t at terrestrial mines.

OSIRIS-REx returned 121.6 grams from C-type asteroid Bennu in September 2023. Analysis in 2025 revealed 14 of 20 amino acids used by life, all five nucleobases (DNA/RNA components), and minerals unseen on Earth. This ground-truth data confirms spectral analysis predictions and provides the first direct characterization of a resource target. NASA's Psyche mission arrives at metal asteroid 16 Psyche in August 2029, providing the first detailed characterization of an M-type body.

Because water for propellant is the first economically viable mining business, C-type asteroids are the near-term targets despite M-type asteroids holding higher per-kilogram value for precious metals. This inversion of intuitive value -- the most abundant asteroid type is the most commercially valuable first -- shapes the entire industry timeline. Companies targeting water (TransAstra, Karman+) are better positioned on the 10-year horizon than those targeting precious metals (AstroForge), though AstroForge's prospecting capability builds essential competencies for later phases.

## Evidence
- OSIRIS-REx returned 121.6g from C-type asteroid Bennu (September 2023), confirming water ice and organic composition
- C-type asteroids comprise 75% of known asteroids with 10-20% water by mass
- NASA Psyche mission targeting M-type asteroid 16 Psyche (arrival August 2029)
- AstroForge, TransAstra, and Karman+ active in second-wave asteroid mining

## Challenges
M-type asteroids may prove more economically accessible sooner if platinum group metal demand spikes from fuel cell adoption or if in-space manufacturing creates demand for structural metals before the propellant economy matures. The water-first thesis depends on propellant depots existing to create demand.

---

Relevant Notes:
- [[asteroid mining economics split into three distinct business models with water-for-propellant viable near-term and metals-for-Earth-return decades away]] — C-type water extraction is the Model A business case
- [[water is the strategic keystone resource of the cislunar economy because it simultaneously serves as propellant life support radiation shielding and thermal management]] — asteroid water feeds the same strategic value chain as lunar water
- [[asteroid mining second wave succeeds where the first failed because launch costs fell 10x spacecraft costs fell 30x and real customers now exist]] — second-wave companies are targeting C-type water extraction

Topics:
- [[space exploration and development]]
