Gwedo: Walk the Moon & Mars

A Solar System trip in your hand.

■ Space flight
Fly between the Sun, the planets and their major moons. Tap a planet or pick it on the route map and autopilot takes you there; a short card opens when you arrive. In free flight a tap guides you there too; move the stick to take over. Beside Earth floats the International Space Station, from NASA's detailed model; near Jupiter, Saturn, the Moon and Neptune you will find NASA's public 3D models of the spacecraft there (Juno, Cassini, LRO, Voyager 2), and "Look closer" flies you in on the Great Red Spot, Saturn's rings, Io's volcanoes and Europa's ice.

■ The Moon · Sea of Tranquility
Walk a landing site rebuilt from records of the plain where Apollo 11 touched down in 1969. A slow, bounding gait tuned to lunar gravity (about one sixth of Earth's), the lander, Earth in the black sky, and five stops (the laser reflector, the flag, the seismometer and more) with NASA photographs. An exhibit lets you look over the Apollo 11 spacesuit (A7L) in photographs.

■ Mars · Jezero Crater
Walk the crater Perseverance is exploring: seven stops, NASA/JPL photographs, Ingenuity, the blue Martian sunset, and a dust devil you can hear (a real Perseverance recording next to a staged sound; Mars's air is so thin it carries almost no sound).

■ Titan · Huygens landing site
Descend through the orange haze to where ESA's Huygens probe landed in 2005, still the only landing in the outer Solar System, and see its real photos of the icy cobbles and river channels.

■ Europa · a virtual landing
Set down on Jupiter's icy moon, where no probe has ever landed (and the app says so). Jupiter hangs in the sky at its real apparent size; switch between day, eclipse and night. Double ridges, chaos terrain and the ocean under the ice, with real Juno and Galileo photos.

■ Follow Voyager 2 · Look over the spacecraft
Ride behind Voyager 2 from its 1977 launch past Jupiter, Saturn, Uranus and Neptune to the edge of the heliosphere in 2018, with Voyager's own photos at each planet. Then turn a 3D Voyager and tap its antenna, nuclear power source, camera platform and the Golden Record.

■ Far space · four galaxies
The Whirlpool, Andromeda, Sombrero and Pinwheel galaxies as explanatory 3D reconstructions you can turn, next to the real Hubble photographs you can zoom into, plus James Webb photos of the Whirlpool and Sombrero.

■ Space telescopes · deep fields
Turn and zoom Hubble and James Webb in real-time 3D; tap the mirror, the sunshield or the solar arrays for notes and narration. See the Hubble Ultra Deep Field, Webb's First Deep Field and both telescopes' view of the same sky up close.

■ Constellations · Orion and the zodiac
Tap a group of stars to draw its shape and open its story; tap a star for its name and brightness. Star positions come from the HYG catalogue (CC BY-SA 4.0).

■ Virtual helmet view
Put the helmet on (the visor slides down and locks) and walk on with the view from inside it, with a gold sun visor. On or off, as you like.

■ Sagittarius A*
A visualization of light bending around the black hole at the center of our galaxy.

■ Listen
Every description has a Listen button with spoken narration by an AI voice (Korean and English, not a real person). Turn the voice off in Settings to read only.

■ How it is made
· Everything works offline. Only the "NASA source" button opens the original page in your browser.
· Distances and sizes are not to scale (shrunk so trips take minutes).
· Landing sites are reconstructions for this experience, not surveyed terrain. Photographs and recordings are real records and are labeled as such; staged scenes and AI-generated sounds are labeled too. Every source is listed on the app's "Sources and rights" screen.
· Korean and English (switch in Settings).
· No ads, no in-app purchases, no sign-in, and no personal data collected.
· This app is an independent work. It is not affiliated with or endorsed by NASA, ESA or the Smithsonian.