NASA's Orion spacecraft is heading home after exiting the lunar sphere of influence.

Orion completed the return powered flyby burn that put the spacecraft on course for splashdown on Sunday. Earth's force of gravity is now the primary gravitational force acting on the spacecraft.

Flight controllers used Orion's cameras to inspect the crew module thermal protection system and European Service Module, the second of three planned external spacecraft inspections.

Teams conducted this survey early in the mission to provide detailed images of the spacecraft's external surfaces after it had flown through the portion of Earth's orbit containing the majority of space debris, and teams reported no concerns after reviewing the imagery.

This second inspection during the return phase is being used to assess the overall condition of the spacecraft several days before re-entry.

Cameras on the four solar array wings have captured a series of still images. Engineers and flight controllers at NASA's Johnson Space Center in Houston will review the imagery over the coming days.

A final photographic survey will be conducted Friday as Orion continues its journey home.

The water cycle is an important part of the controlled ecological life support system (CELSS). It involves the supply of drinking water and plant irrigation water, and the recycling of urine, sanitary waste water, and air condensate water. Using urine and sanitary wastewater for plant irrigation is an effective form of wastewater reuse, but there are three main challenges.

Firstly, some salt content in wastewater, especially sodium chloride, is high, but it is not necessary for plant growth and may inhibit plant growth.

Secondly, the wastewater contains organic components such as surfactants, which also have a negative impact on plant growth.

Thirdly, if wastewater is used as the main nutrient source, the proportion of mineral elements in wastewater might be inconsistent with the proportion the plant growth needs, which will also affect the normal growth of plants.

After 908 days in low Earth orbit, a small package on board the X-37B Orbital Test Vehicle-6 has come home to the delight of some biological scientists. Soon they will open an aluminum alloy container that holds samples of plant seeds that they hope can be used to sustain astronauts on long duration missions to the moon, Mars, and beyond.

Officially, it is known as a SEER experiment, short for Space Environment Exposure Research, a pathfinder mission supported by NASA's Biological and Physical Sciences Division (BPS) in collaboration with the US Air Force.

Unofficially, they're referred to as the "Thrive in Space" experiments—a way to underscore the stepping-stone research that scientists are undertaking to help advance their fundamental understanding of what it takes to grow and protect plants beyond our planet.