Scientists have measured the mass and size of the first Mars-sized exoplanet named Kepler-138b.

The planet is about 200 light years from our solar system and is one of three planets that orbit a red dwarf star Kepler-138.

Kepler-138b’s mass is less than 1/10th that of Earth’s and it is half the size of the Earth. In kilograms, Kepler-138b is 4 followed by 23 zeros (4 times 10 to the power of 23 kilograms). In kilometers, its diameter is about 6,600.

Study’s lead researcher Daniel Jontof-Hutter at Penn State said that each time a planet transited the star it blocked a small fraction of the star's light. This allowed them to measure the size of the planet.

The research was also led by astronomers at NASA Ames Research Center, the SETI Institute, and the University of Chicago.

The researchers added that that they also measured gravity of all the three planets, using data from NASA's Kepler mission and observing the times of each transit precisely.

According to coauthor Jason Rowe, the measurements were consistent with a variety of compositions, and favor compositions that were mostly rocky.

Eric Ford, coauthor of the study, mentioned that the results reveal the rapid progress of exoplanet science.

The exoplanet could shed light on the kinds of small, rocky worlds that might be found around distant stars. It could also reveal whether these planetary systems are similar, or very different, from our own inner solar system.