Space tourism company Virgin Galactic announced Monday that it is resuming flights with a mission this month, its first in nearly two years, and the launch of commercial trips in June.

The Unity 25 mission will take place in late May with four company employees on board, said Virgin Galactic, which was founded by British billionaire Richard Branson, who took part in the firm's last spaceflight in July 2021.

"Unity 25 is the final assessment of the full spaceflight system and astronaut experience before commercial service opens in late June," Virgin Galactic said in a statement.

Unity 25 will be the company's fifth trip into space, defined as 50 miles (80 kilometers) above sea level.

Unlike other companies that use vertical-launch rockets, Virgin Galactic uses a carrier aircraft that takes off from a runway, gains high altitude, and drops a rocket-powered plane that soars into space before gliding back to Earth.

No matter where we go in the universe, we're going to need water. Thus far, human missions to Earth orbit and the moon have taken water with them. But while that works for short missions, it isn't practical in the long term. Water is heavy, and it would take far too much fuel to bring sufficient water to sustain long-term bases on the moon or Mars. So we'll have to use the water we can extract locally.

Fortunately, water is a common molecule in the universe. Even the moon has plenty of water to sustain a lunar colony. The only real challenge is how to extract it. As a recent study published in Acta Astronautica shows, that might be as easy as popping things into a microwave oven.

Although water is present in tiny quantities all over the moon, it is most concentrated in the polar regions.