It actually can see the solar system. But using a telescope built to catch single photons from the dawn of time to look at Mars is like staring into a floodlight with night vision.
Despite the challenge, the James Webb Space Telescope (JWST) has already captured detailed images of the local cosmic backyard, including Jupiter, Mars, Neptune, and Uranus.
While it was built for deep space, there are only two major constraints on what JWST can observe locally: its operating temperature and the brightness of nearby planets.
First, JWST cannot look at the Sun, Earth, Mercury, or Venus. The telescope's instruments are optimized to detect faint infrared light—heat—from the early universe. To do this, the detectors must be kept near absolute zero (about minus 370 degrees Fahrenheit). JWST orbits the Sun from a position called Lagrange Point 2, keeping Earth and the Sun in the same general direction. Its tennis-court-sized sunshield always faces this direction, acting as a permanent parasol. Turning the optics back toward the inner solar system would expose the delicate sensors to solar radiation, damaging them permanently.
Second, the outer planets it can see are millions of times brighter than distant galaxies.
To safely capture these targets without saturating its detectors, JWST operators use exposure times of fractions of a second. When targeting Jupiter, the telescope tracked the fast-moving planet and recorded details invisible to optical telescopes, such as glowing auroras at the poles, high-altitude atmospheric hazes, and the planet's faint, dusty ring system.
Rather than being unable to view the solar system, JWST maps the chemical composition of planetary atmospheres and spots weather patterns on nearby worlds between its deep-space observations.