79°30′00″ S · 0°00′00″ E
The geological solution — high on a massif summit in the far-southern highlands near Newton crater, where the mountain underfoot lifts the camera's line of sight clear of the rugged terrain so Earth never sets.
The site
High on a massif summit, near Newton crater
This site sits high on a massif summit in the far-southern highlands, near Newton crater, in rugged, heavily cratered terrain on the sub-Earth meridian. Newton — the deepest crater on the Moon's near side — lies about 135 km to the north-northwest, with Short and Moretus further toward the equator and Cabeus and Malapert toward the pole.
| Coordinate | Decimal degrees | Degrees-minutes-seconds |
|---|---|---|
| Latitude | 79.50° S | 79° 30′ 00″ S |
| Longitude | 0.00° E | 0° 00′ 00″ E |
This site sits comfortably inside the geometric always-visible zone — more than three degrees from its edge — so Earth rides higher and more securely here than at the northern site, and it works because the camera stands on the summit of a high massif that lifts its line of sight clear of the rugged southern terrain.
Because this site lies in the Moon's southern hemisphere, Earth sits due north here — the 180° mirror image of the northern site, where Earth stands due south. It is the same low, never-setting planet, framed over the opposite horizon.
Where it is
The southern site on the map
Other passing candidates
Other southern locations
The other southern locations that keep the entire Earth disk permanently visible (full-disk passers). The clearance margin shown is the full-disk margin (the stricter test). All southern passers carry robust margins (combined uncertainty 0.05°).
| Coordinates | Earth elevation range | Clearance margin (full-disk) | Binding terrain feature |
|---|---|---|---|
| 83.00°S, 25.0°W | −1.23° … +13.25° | +1.23° | deeply depressed horizon −3050 m at 87.5 km (az 33°) |
| 82.00°S, 20.0°E | −0.02° … +14.39° | +0.58° | depressed horizon −598 m at 46.5 km (az 334°) |
| 80.50°S, 10.0°W | +1.93° … +16.08° | +0.29° | ridge +2108 m at 61.2 km (az 11°) |
| 80.50°S, 5.0°W | +2.15° … +16.10° | +1.11° | ridge +602 m at 37.2 km (az 357°) |
| 80.00°S, 15.0°E | +2.12° … +16.49° | +0.88° | ridge +759 m at 42.5 km (az 338°) |
| 79.00°S, 25.0°W | +2.14° … +17.05° | +0.21° | ridge +756 m at 19.3 km (az 22°) |
| 79.00°S, 20.0°W | +2.62° … +17.31° | +3.42° | depressed horizon −203 m at 100 km (az 28°) |
| 79.00°S, 15.0°W | +3.02° … +17.48° | +1.50° | distant rim +3022 m at 86.2 km (az 23°) |
| 79.00°S, 5.0°W | +3.61° … +17.60° | +1.51° | ridge +1196 m at 34.5 km (az 357°) |
| 79.00°S, 5.0°E | +3.61° … +17.60° | +1.59° | ridge +709 m at 26.6 km (az 348°) |
| 79.00°S, 25.0°E | +2.17° … +17.07° | +0.20° | ridge +766 m at 29.1 km (az 328°) |
Closest to this site's latitude band: the cluster of sites at 79.00°S is nearest (half a degree away), with 80.00°S and 80.50°S close behind. Most robust margin: by a clear distance the sturdiest is 79.00°S/20.0°W at +3.42°, where a distant depressed horizon leaves Earth a wide berth. Note that several locations deeper toward the south pole also pass — 83.00°S/25.0°W and 82.00°S/20.0°E, both perched about 3 km up on South Pole–Aitken massifs — but along the exact sub-Earth meridian itself the southernmost location that still clears is this one at 79.50°S; further south on the meridian, the terrain wins. That is the reason a high massif summit, rather than a deeper latitude, is what makes the southern leg work.
In plain language
What this site actually is
The EXAX project sets out to put one camera on the Moon's surface and keep it aimed at Earth without pause — a fixed vantage point on solid ground that holds the entire planet in view for years, producing a continuous record of Earth seen whole, the way no orbiting satellite can.
Choosing where to put it is less obvious than it sounds. Because the Moon keeps almost the same face turned toward us, it seems as though Earth must sit still in the lunar sky and nearly any near-side location would work. In practice the Moon rocks gently as it orbits, a slow wobble that nudges Earth's apparent position around the sky over a rhythm of about 18.6 years. Toward the edges of the visible face, that motion can carry Earth down near the horizon, where even a modest hill or crater rim might cut across the view. Keeping the planet permanently visible therefore means locating a spot where Earth clears the local landscape at every moment of the full multi-year cycle. Finding it required a four-part study: first pinning down precisely where Earth sits in the sky from each candidate point through the whole wobble, then testing that against the real shape of the Moon's surface, measured by laser altimeter from orbit, to be sure no nearby terrain ever blocks the planet.
This location lies deep in the Moon's rugged far south, on the line pointing most directly at Earth, in the heavily cratered highlands near Newton — the deepest crater on the side of the Moon that faces us. What sets the spot apart is height: the camera would stand on the summit of a tall mountain massif, raised more than two kilometres above the broken country around it.
From this summit Earth never rises and never sets. It stands clear in one part of the sky, higher and more securely above the horizon than at the project's northern site, and simply stays there. Earth appears as a large, dazzling sphere — about three to four times the width of a full Moon and far brighter — and it shifts only slowly, drifting in a small loop over the course of each month while remaining in the same quarter of the sky year after year. The camera would record the planet rotating once a day, its continents, oceans, storms and the moving boundary between daylight and darkness all passing through the frame. Earth also cycles through phases like the Moon does for us, from crescent to full and back, about once a month.
The single remaining step before this candidate becomes a real camera site is a detailed close-range survey of the summit and the terrain toward Earth, fine enough to confirm the exact horizon shape and the precise height of the chosen spot, so the camera's clear line to Earth is locked in.
More
Sources and related pages
The full positional-astronomy and terrain-clearance analysis — ephemeris basis, terrain models, and the complete source record behind this site — is documented in the downloadable science dossier.