both the N1 Rocket and the LK Lunar Module programs without any further development. Proposed landers Altair (spacecraft), a proposed spacecraft for the Constellation program previously known as the Lunar Surface Access Module Lunar Lander (space mission), an ESA mission to send an autonomous lander to the Moon Lunar Lander Challenge, a competition to produce VTVL vehicles with sufficient delta-v to fly from the Moon to orbit Luna-Glob, a lunar exploration program by the Russian Federal Space Agency Lockheed Martin Lunar Lander, proposed lunar lander for Moon Missions under Project Artemis. Mighty Eagle lander (previously called NASA Robotic Lunar Lander) current NASA program for developing a new generation of small, autonomous lunar landers Project Morpheus, a NASA research and development program test bed XEUS A human rated lunar lander being developed by United Launch Alliance and Masten Space Systems Boeing Lunar Lander is a proposal for a human landing system for NASA's Artemis program Blue Origin, Lockheed Martin, Northrop Grumman and Draper Laboratory proposed a human landing system for NASA's Artemis program Human landers under development On April 16, 2021, NASA announced a US$2.89 billion firm-fixed price contract with SpaceX for an uncrewed and subsequent crewed mission to the Moon using Starship HLS. Challenges unique to lunar landing Landing on any Solar System body comes with challenges unique to that body. The Moon has relatively high gravity compared to that of asteroids or comets—and some other planetary satellites—and no significant atmosphere. Practically, this means that the only method of descent and landing that can provide sufficient thrust with current technology is based on chemical rockets. In addition, the Moon has a long solar day. Landers will be in direct sunlight for more than two weeks at a time, and then in complete darkness for another two weeks. This causes significant problems for thermal control. Lack of atmosphere space probes have landed on all three bodies other than Earth that have solid surfaces and atmospheres thick enough to make aerobraking possible: Mars, Venus, and Saturn's moon Titan. These probes were able to leverage the atmospheres of the bodies on which they landed to slow their descent using parachutes, reducing the amount of fuel they were required to carry. This in turn allowed larger payloads to be landed on these bodies for a given amount of fuel. For example, the 900-kg Curiosity rover was landed on Mars by a craft having a