The team confirmed the observation using data from NASA's Spitzer Space Telescope and a technique called BLENDER that ruled out most false positives.

[5][1][7] For comparison, the Earth's oceans represent only 0.02% of our planet's mass,[8] with an additional amount potentially a few times this stored in the mantle.

[1] An additional, longer-period dimming was detected in Kepler-10's spectrum, suggesting that a second planet existed in the system; however, there remained the possibility that this signal could have some other cause, and that the transit event was a false positive.

[1] Attempts to measure the radial velocity effects of this object, then named KOI 072.02, were fruitless; therefore, to rule out false positive scenarios, the Kepler team used a technique called BLENDER.

[1] The application of BLENDER was supplemented by use of the IRAC instrument on the Spitzer Space Telescope, which was used on August 30 and November 15, 2010, to further define Kepler-10's light curve at the point where KOI 072.02 appeared to transit it.

Keck Observatory, ruled out the possibility that a nearby star's light was corrupting the observed spectrum of Kepler-10 and creating the results that had led astronomers to believe that a second planet existed in Kepler-10's orbit.

The BLENDER technique allowed the Kepler team to rule out the majority of the alternatives including, notably, that of triple star systems.

[5][7] However, in July 2017, more careful analysis of HARPS-N and HIRES data showed that Kepler-10c was much less massive than originally thought, instead around 7.37 (6.18 to 8.69) ME with a mean density of 3.14 g/cm3.

Instead of a primarily rocky composition, the more accurately determined mass of Kepler-10c suggests a world made almost entirely of volatiles, mainly water.