Planet masses can sometimes be deduced via transit timing variations, but again, it works best for tightly packed systems, i.e. the inner planets of Kepler 186.
The planets' masses have not been constrained with radial velocity or transit timing measurements (Quintana et al. 2014). Table 3 shows the range of plausible planetary masses assuming a range of compositions: 100% ice, 50% ice/ 50% rock, Earth-like composition, and 100% iron (following Fortney et al. 2007).
Table 3 gives planet f about 1.5 Mearth with an Earth-like composition.
One interesting point from the paper is that it is quite possible that there is a planet between e and f. An additional planet actually made their system formation models work better, and they found such a planet could plausible be inclined enough not to transit.If it does exist, they put it around ~0.2 AU, which would be right around the inner edge of the habitable zone.
Each of the nine fields planned for study in the next two years are in the zodiacal constellations and contain between 10,000 and 20,000 stars for observations by Kepler's telescope. The K2 mission's 100,000 targets also include the very bright cores of galaxies, supernovae, asteroids and Neptune, plus aging stars identified as candidates for research into the convective processes inside stars, a field known as astroseismology.
Astrobiology has revealed new discoveries about our world and the solar system. Living organisms thrive in harsher environments on Earth than we ever previously imagined. Microbial biodiversity and extremophile life are now known to be ubiquitous and abundant. Beyond Earth, science has identified more than 1,400 exoplanets. That life thrives in multifarious conditions, coupled with these potentially habitable exoplanets and the detection of life-giving elements on numerous moons on asteroids, means we must face the possibility that simple or complex organisms may be discovered beyond Earth. How might we prepare for such a discovery? Baruch S. Blumberg NASA/Library of Congress Chair in Astrobiology Steven J. Dick convenes scientists, historians, philosophers and theologians from around the world for a two-day symposium at the Library of Congress to explore how we prepare to face new knowledge that may challenge our very conceptions of life and our place in the universe.
NASA's Kepler Space Telescope, despite being hobbled by the loss of critical guidance systems, has discovered a star with three planets only slightly larger than Earth. The outermost planet orbits in the "Goldilocks" zone, a region where surface temperatures could be moderate enough for liquid water and perhaps life, to exist.The star, EPIC 201367065, is a cool red M-dwarf about half the size and mass of our own sun. At a distance of 150 light years, the star ranks among the top 10 nearest stars known to have transiting planets. The star's proximity means it's bright enough for astronomers to study the planets' atmospheres to determine whether they are like Earth's atmosphere and possibly conducive to life."A thin atmosphere made of nitrogen and oxygen has allowed life to thrive on Earth. But nature is full of surprises. Many exoplanets discovered by the Kepler mission are enveloped by thick, hydrogen-rich atmospheres that are probably incompatible with life as we know it," said Ian Crossfield, the University of Arizona astronomer who led the study.A paper describing the find by astronomers at the University of Arizona, the University of California, Berkeley, the University of Hawaii, Manoa, and other institutions has been submitted to Astrophysical Journal and is freely available on the arXiv website.