Lunar Reconnaissance Orbiter, studying the Moon in high detail

Highlights

• The features you see on the Moon’s surface formed billions of years ago after asteroids and comets bombarded the inner solar system, possibly bringing water and the ingredients for life to Earth.
• NASA’s Lunar Reconnaissance Orbiter, or LRO, studies the Moon to help piece together what happened.
• LRO also hunts water ice in permanently shadowed craters near the Moon’s poles. Its 2009 ride-along spacecraft detected water in the debris plume created by a rocket stage deliberately crashed into the south pole.

What is the Lunar Reconnaissance Orbiter?

The Moon’s splotchy features tell an important story. After the Moon formed 4.5 billion years ago, asteroids and comets pummeled the inner solar system, possibly bringing water and the ingredients for life to early Earth. These objects scarred the Moon, along with later volcanic eruptions and meteor impacts, creating a well-preserved record of our solar system’s origin story hanging in the night sky.

NASA’s Lunar Reconnaissance Orbiter, LRO, is a key tool for deciphering that story. From lunar orbit, it maps the Moon’s surface and composition to help scientists figure out the chain of events that created the Moon we see today. LRO also studies the Moon’s polar regions, where water ice exists in permanently shadowed craters. This is important not only from a scientific perspective—how did the water get there, and how does it relate to Earth’s water?—but also for future human explorers that could mine the ice for air, water, and rocket propellant.

LRO launched in 2009 on a mission to create high-resolution topography maps for future NASA astronauts under the agency’s now-canceled Constellation program. It completed that task in 2010 and was transferred to NASA’s science division, though data the spacecraft collects is still vital for planning future exploration missions.

Sharing the rocket ride to the Moon was LCROSS, the Lunar CRater Observation and Sensing Satellite. Mission planners deliberately crashed the rocket’s upper stage near the Moon’s south pole, kicking a 350-ton plume of debris into space. LCROSS flew through the plume and found a water content of 5.6% before impacting a few minutes after the rocket stage.

How does the Lunar Reconnaissance Orbiter study the Moon?

LRO is equipped with 7 science instruments, the most well-known of which is a 195-millimeter (7.7-inch) telescope and camera system that can see details up to 2.5 meters across. The cameras have captured views of the Apollo sites so detailed you can see astronauts’ footprints, stunning crater rims that experience near-constant sunlight, and strange pits that could lead to subsurface lava tubes. In 2015 it snapped an iconic new Earthrise image.

LRO is equipped with a laser altimeter that produces 3D maps by shooting lasers at the surface and measuring reflection times. The spacecraft also carries two instruments suited to peering into dark craters to search for signs of water ice, and a temperature instrument that led to the discovery of the coldest place in the solar system.

Learn more

• Read about Earth's Moon
• Every mission to the Moon, ever
• The history of the Moon in 2.5 minutes