K2-148b
K2-148b is a confirmed Super-Earth, probably rocky, closely orbiting a small orange dwarf star. It is the innermost of three Super-Earths around the star K2-148, which is in a wide binary pair with the M0.5V red dwarf EPIC 220194953. K2-148b is the smallest planet of the system, at about a third larger than Earth, and could be terrestrial in nature. However, the three planets do not exhibit significant transit timing variations, implying that they could have relatively low masses. The planet was validated in early 2018 by Hirano "et al." and is too hot for known life.
Planetary habitability
"Low mass" is partly a relative label: the Earth is low mass when compared to the Solar System's gas giants, but it is the largest, by diameter and mass, and the densest of all terrestrial bodies. It is large enough to retain an atmosphere through gravity alone and large enough that its molten core remains a heat engine, driving the diverse geology of the surface (the decay of radioactive elements within a planet's core is the other significant component of planetary heating). Mars, by contrast, is nearly (or perhaps totally) geologically dead and has lost much of its atmosphere. Thus it would be fair to infer that the lower mass limit for habitability lies somewhere between that of Mars and that of Earth or Venus: 0.3 Earth masses has been offered as a rough dividing line for habitable planets. However, a 2008 study by the Harvard-Smithsonian Center for Astrophysics suggests that the dividing line may be higher. Earth may in fact lie on the lower boundary of habitability: if it were any smaller, plate tectonics would be impossible. Venus, which has 85% of Earth's mass, shows no signs of tectonic activity. Conversely, "super-Earths", terrestrial planets with higher masses than Earth, would have higher levels of plate tectonics and thus be firmly placed in the habitable range.