First came the darkening skies, then the crescent-shaped shadows on the ground, and finally an eruption of cheers by crowds that gathered Saturday along the narrow path of a rare "ring of fire" eclipse of the sun.

It was a spectacular show for millions of people across the Americas as the moon moved into place and the ring formed.

There were hoots, hollers and yelps for those with an unfettered view in Albuquerque, where the celestial event coincided with an international balloon fiesta that typically draws tens of thousands of spectators and hundreds of hot air balloon pilots from around the world.

After spending more than a year in space, Frank Rubio now has to get used to that pesky thing Earthlings call gravity.

"Walking hurts a little bit the first few days, the soles of your feet and lower back," he said at a news conference Friday at NASA's Johnson Space Center in Houston, Texas.

Throughout the 20th century, multiple proposals have been made for the crewed exploration of Mars. These include the famed "Mars Project" by Werner von Braun, the "Mars Direct" mission architecture by Robert Zubrin and David Baker, NASA's Mars Design Reference Mission studies, and SpaceX's Mars & Beyond plan. By 2033, two space agencies (NASA and the CNSA) plan to commence sending crews and payloads to the Red Planet. These and other space agencies envision building bases there that could eventually lead to permanent settlements and the first "Martians."

This presents several major challenges, not the least of which have to do with exposure to radiation, extreme temperatures, dust storms, low atmospheric pressure, and lower gravity. However, with the right strategies and technology, these challenges could be turned into opportunities for growth and innovation. In a recent paper, a Leiden University researcher offers a roadmap for a Martian settlement that leverages recent advancements in technology and offers solutions that emphasize sustainability, efficiency, and the well-being of the settlers.