The challenge of explaining dark matter, a substance that emits no electromagnetic signal and cannot be directly imaged, is the central scientific target NASA has assigned to its Roman Space Telescope, a $4.3 billion observatory. The mission is also expected to discover thousands of planets beyond our solar system.
Dark matter is thought to account for the majority of all matter in the universe. It shapes the motion of galaxies and the clustering of large-scale cosmic structure through gravitational effects on visible matter, yet it has never been directly observed because it does not interact with light in any part of the electromagnetic spectrum. What it is made of remains one of the fundamental open questions in physics. Roman is expected to advance that search.
The exoplanet component is a census problem. Thousands of worlds orbiting stars outside our solar system are expected to be found through the mission. Ground-based observatories face a physical constraint here: Earth's atmosphere absorbs and distorts incoming light before it reaches a detector, cutting sensitivity at the faint signal levels that exoplanet detection requires. An orbital telescope bypasses that layer entirely.
Roman's scope, as NASA frames it, is to scan the universe. The mission expects to add thousands of exoplanets to the known catalogue of worlds beyond our solar system.