Caves were some of humanity's first shelters. Who knows what our distant ancestors were thinking as they sought refuge there, huddling and cooking meat over a fire, maybe drawing animals on the walls. Caves protected our ancient ancestors from the elements, and from predators and rivals, back when sticks, stones, furs and fire were our only technologies.

So there's a poetic parallel between early humans and us. We're visiting the moon again, and lunar caves could shelter us the way caves sheltered our ancestors on Earth.

On the moon, astronauts will need protection from a different set of hazards. They'll have to contend with cosmic and solar radiation, meteorites, wild temperature swings, and even impact ejecta.

Spain's trio of ANSER CubeSats, due to fly on Europe's next Vega launcher, will fly like a flock of birds in orbit—in more ways than one. Keeping in formation by following their leader, the three shoebox-sized satellite will image Iberian waters as if they are a single standard-sized mission. And they will unfurl wing-like flaps to maintain their relative positions, surfing on the scanty airflow at the top of Earth's atmosphere.

ANSER—Advanced Nanosatellite Systems for Earth-observation Research—is a cluster of three CubeSats which will work together in close vicinity as if they are a single satellite. Due to be launched on Europe's next Vega flight, VV23, the ANSER mission is being undertaken by INTA, the Spanish Institute of Aerospace Technology.

Santiago Rodriguez Bustabad, overseeing the mission, explains, "ANSER is also the Latin name for the wild goose, a good example of birds flying in formation, adopting a leader-follower protocol, which is what our mission is emulating."

These three-unit CubeSats will orbit around 500 km altitude, maintaining formation at an optimum 10 km apart from each other. But they do not have any onboard propulsion systems.