No one has visited the moon since 1972. But with the advent of commercial human spaceflight, the urge to return is resurgent and generating a new space race. NASA has selected the private company SpaceX to be part of its commercial spaceflight operations, but the firm is also pursuing its own space exploration agenda.

To enable flights to the moon and beyond, both NASA and SpaceX are developing new heavy lift rockets: SpaceX's Starship and NASA's Space Launch System.

But how do they differ and which one is more powerful?

Starship

Rockets go through multiple stages to get into orbit. By discarding spent fuel tanks while in flight, the rocket becomes lighter and therefore easier to accelerate. Once in operation, SpaceX's launch system will be comprised of two stages: the launch vehicle known as "BFR" (Big Falcon Rocket) and the Starship.

BFR is powered by the Raptor rocket engine, burning a combination of liquid methane and liquid oxygen.

With a suite of new national and international spacecraft primed to explore the Red Planet after their arrival next month, NASA's MAVEN mission is ready to provide support and continue its study of the Martian atmosphere.

MAVEN launched in November 2013 and entered the Martian atmosphere roughly a year later. Since that time, MAVEN has made fundamental contributions to understanding the history of the Martian atmosphere and climate. A few science highlights include:

• Determination that the bulk of the Martian atmosphere has been lost to space through time, driving changes in the Mars climate and the ability to support life at the surface.
• Characterization of the mechanisms by which gas is stripped away from the atmosphere to space and of the role of solar storms hitting Mars in enhancing the escape rate.
• There is significant unexpected variability in the loss rate of hydrogen to space through the seasons, which has important implications for the history of water.