Planetary systems containing terrestrial, transiting, low-mass exoplanets with mass M_p ≤ 4 M_⊕ and radius constrained to a precision better than 12% are shown relative to the location of the estimated habitable zone (blue-shaded area, Kopparapu et al. 2014). GJ7 and the Solar System are depicted at the top and bottom, respectively. All planetary systems are scaled to GJ7. The size of the black dots is linearly scaled to the radius of the planets (excluding the Solar System). The semimajor axis errors are plotted, and the x-axis is on a logarithmic scale.