This isotope is found at a ratio of about one per 2,500 helium-4 ions, the latter being the common version of helium.

"More images below of the horizon glow that comes to life just above the Moon's surface as the sun goes down. This milestone embodies all the achievements from this historic Firefly mission.

On March 29, a partial solar eclipse will cast a shadow on the sun for people in the Northeast. See when, where and how to look.

New evidence found by scientists supports a theory as to what exactly is inside the moon ... based on how the moon responds ...

The sun has set on the Blue Ghost spacecraft ... The experiment gathered data about naturally occurring currents inside the moon, which provides hints about what the moon is made of down to ...

The Blue Ghost lunar lander, which has been on the moon since the spacecraft’s successful touchdown on March 2, captured images of the sun, Earth and moon lined up at around 4:30 a.m. ET ...

A new image has emerged of the Red Planet rising above the lunar limb after being occulted by the moon in January.

NASA explains: "A lunar eclipse occurs when the Sun, Earth, and Moon align so that ... During totality, the entire moon is inside Earth's umbra, turning a deep red or orange color.