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.

Antarctica's McMurdo Dry Valleys contain some of Earth's coldest and driest deserts. The environment there is so extreme that the Dry Valleys have been used as Mars analogs to test prototype equipment for future Mars exploration.

To survive these harsh conditions, layers of algae and bacteria in the Dry Valleys overwinter in a freeze-dried state, coming back to life in the summer when neighboring glaciers melt and water flows down the stream channels again.

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.

The Orion spacecraft on the Artemis I mission is carrying, as part of the MARE experiment, two human "phantoms" equipped with numerous cosmic rays detectors. The information gathered by the detectors will for the first time verify the knowledge, crucial for the presence of humans in deep space, of the effects of cosmic rays on the health of the astronauts who are to live and work in an environment devoid of the protective effects of our planet's magnetosphere.

Of the numerous dangers lurking for astronauts undertaking long-distance space travel, among the most serious and at the same time the most difficult to eliminate, is exposure to harmful doses of cosmic radiation. Data collected during the MARE experiment (MATROSHKA AstroRad Radiation Experiment) will help ensure the safety of future deep space pioneers.