A recent JWST program has measured the thermal emission of two rocky exoplanets orbiting the nearest M dwarf, LTT 1445 A, located only 6.9 pc from Earth. The data show eclipse depths of 157 ppm for planet b (±18 ppm) and 154 ppm for planet c (±54 ppm). These depths translate into 15‑µm brightness temperatures of 528 K for planet b and 625 K for planet c, temperatures that match a bare, rocky surface with little to no atmosphere.

The analysis combined three independent data reductions with all existing JWST photometry and 220 spectroscopic radial‑velocity measurements. This joint approach sharpened the measurements of the planets’ radii, masses and orbits by a factor of 1.6 to 2.3. For planet b, Bayesian retrievals using these data and an archival MIRI/LRS spectrum constrain any CO₂ partial pressure to less than 0.6 mbar and the surface pressure to below 0.1 bar, and forward models rule out thick aerosol layers. The conclusion is that planet b has no substantial atmosphere.

Planet c’s eclipse depth is less secure because the eclipse may be grazing and overlaps with other events, leaving the depth poorly constrained. The only robust conclusion for planet c is that very thick, CO₂‑rich atmospheres (≥1 bar with ≥1 % CO₂) are ruled out.

These results place the two planets on the lower end of expected atmospheric retention for rocky worlds around M dwarfs. Planet b, the one closest to the “Cosmic Shoreline” where extreme ultraviolet irradiation can strip atmospheres, shows no atmosphere, indicating that the shoreline cannot lie far beyond the airless side. The study demonstrates how precise secondary‑eclipse measurements with JWST can probe the atmospheric states of small exoplanets even around faint host stars.