Hazard Fingerprints

Twelve fingerprints

Hazard fingerprints on seven shared bars.

A hazard accumulates, has a rate or a return period, and is defended against at a price in mass, power or time. Each figure scores the same seven hazards at one site from 0 to 5, and each bar takes the color of its own value's confidence.

Observed Building Projected Modeled Confidence scale

Reading the bars

Three radiations, never lumped.

Galactic cosmic rays (GCR), solar particle events (SPE) and trapped radiation behave differently enough to get separate bars. GCR is chronic and nearly unshieldable at spacecraft mass; it rises slightly with distance from the Sun as solar modulation weakens. SPE is acute, arrives in hours, and falls with the square of distance - Mercury takes about 6.6 times Earth's fluence, Ceres about an eighth. Trapped radiation belongs to a planet's magnetic field and to particular orbits: the South Atlantic Anomaly in LEO, the Jovian belts that make Europa uninhabitable and leave Callisto, outside them, at roughly 0.1 mSv a day.

The measured surface doses anchor the scale. Chang'e-4's Lunar Lander Neutron and Dosimetry experiment (LND) recorded 1.37 mSv/day on the lunar far side; the Mars Science Laboratory's Radiation Assessment Detector (RAD) recorded about 0.64 mSv/day at Gale crater and 1.84 mSv/day in cruise. Everything else on the page is modeled from those figures, the overhead column and the site's distance from the Sun.

Two destinations break the radiation pattern entirely. Venus at 50-55 km carries roughly half of Earth's sea-level atmospheric shielding overhead, and Titan's surface carries about 10.7 times Earth's - the only outer-system surface where radiation is not a design case. Both trade it for chemistry: sulfuric acid aerosol at Venus, a 94 K nitrogen atmosphere at 1.45 bar at Titan that would burn with any oxygen a crew brought along.

Earth orbit's tallest bar is impact flux, the one hazard that grows with the regime's own success. Dust is the Moon's: abrasive, electrostatically charged regolith that Apollo crews tracked into the Lunar Module and that every landing throws up to about 99 km on ballistic arcs. Mars carries the longest return period with a known date - the 2018 planet-encircling dust storm ended NASA's Opportunity rover, and storms of that class recur roughly every third Mars year.

Several values sit on a single measurement. Triton's nitrogen plumes rest on Voyager 2's 1989 flyby; Pluto's seasonal atmospheric collapse on New Horizons' 2015 pass and occultation records since 1988; Mercury's ICME-driven magnetopause compression on MESSENGER. BepiColombo's Mercury Planetary Orbiter and Mio begin science operations in early 2027, and ESA's JUICE and NASA's Europa Clipper both reach the Jovian system by 2031.

The seven bars

What each bar measures and how it is scored.

• GCR - chronic galactic cosmic ray dose at the unshielded site. 0 under 0.1 mSv/day; 1 to 0.5; 2 to 1.0; 3 to 1.5; 4 to 2.0; 5 above.
• SPE - acute solar particle event exposure, scaled by distance and local shielding.
• Trapped - radiation belts at the site's orbit or surface.
• Impact - micrometeoroid, debris, ejecta or interstellar grain flux.
• Dust - particulate and electrostatic environment: abrasion of seals, bearings, optics and lungs, and surface charging.
• Atmos - atmosphere and chemistry: toxicity, corrosion, pressure, and cryogenic contact temperature.
• Events - episodic events and how often they return: storms, ICMEs, plumes, collapse.

Values

The site values behind the bars.

Record

Provenance.