NASA's Artemis program has one tower standing and one just getting started.

Mobile launcher 1 (ML-1), which endured some significant damage after its use on the Artemis I mission last November, has been undergoing repairs and enhancements in preparation for its reuse on next year's planned Artemis II flight, the first with humans on board.

NASA stuck the 380-foot-tall structure atop its slow-moving crawler-transporter 2 on Wednesday at Kennedy Space Center to begin its two-day return to Launch Pad 39-B.

ML-1 is the ground structure that holds NASA's powerful Space Launch System rocket, and for Artemis II, NASA has been working to add essential features for the four humans that will be riding in the Orion capsule atop the rocket. It will make its way into the Vehicle Assembly Building for eventual stacking of all the rocket parts early next year.

For now, though, it has work planned at the launch site where NASA's Exploration Ground Systems team will perform tests and work on upgrades for both the launcher and the launch pad. That includes a launch day demonstration for the Artemis II crew of NASA astronauts Reid Wiseman, Victor Glover, Christina Koch and Canadian astronaut Jeremy Hansen as well as NASA's closeout crew and the rescue team.

Human missions to Mars will require a substantial launch vehicle to ascend from Mars to rendezvous with a waiting Earth return vehicle in Mars orbit. For an ascending crew of 6, the current best estimate of oxygen propellants required for ascent is about 30 metric tons. Producing oxygen for ascent propellants and possibly life support from the indigenous CO₂ on Mars, rather than bringing oxygen to Mars from Earth, is of significant benefit.

The oxygen production is accomplished through a process known generically as in situ resource utilization (ISRU). Since the Mars Oxygen ISRU Experiment (MOXIE) Project demonstrated operation of a prototype electrolysis system for converting Martian CO₂ to O₂ on Mars with great success, it is now appropriate to investigate scaling up this prototype to a full-scale system.

In a research paper recently published in Space: Science & Technology, Donald Rapp and Eric Hinterman modeled the performance of a full-scale Mars in situ resource utilization (ISRU) system to produce 30 metric tons of liquid O₂, operated for 14 months as the Mars environment changes diurnally and seasonally.

Just how dark is the night sky?

If you step outside during a moonless night and look up, it probably doesn't look that dark at all. Streetlights or nearby porch lights fill the air with a background glow, particularly if they happen to be bluish-white LEDs. Light pollution in your neighborhood is likely so bad that you can only see a few bright stars. Even in somewhat rural areas, our skies are so bright that the Milky Way isn't really visible. In North America and Europe, only about a quarter of children have seen the Milky Way.

To get away from all the light pollution you need to travel to a pretty remote corner of the world. One of the most remote is the Andean desert in Chile.