Notes
Tuesday, 22 September 2026 · PlanetaryFormation.com
Two scars
Valles Marineris is a rift beside that rise.
Mars
Valles is a rift beside a rise. Mariana is a trench.
Valles Marineris runs about 4,000 kilometres east of Tharsis. Typical width is about 200 kilometres; locally it opens toward 600. Usual depth is about 7 kilometres; some walls drop near 10. Mariana is shorter, narrower, and deeper. Challenger Deep is about 10.94 kilometres. As a fraction of each planet’s radius the two scars are close. As factories they are not.
One is a rift beside a plume load. The other is a slab going down. Earth’s nearest living match is a rift beside a swell — East Africa, not the Andes.
This site reads Io through Mars as consecutive stages of one kind of planet, with living Earth as the present chapter. A crack of this length next to that load is what a stagnant lid does when the rise is too heavy. The missions do not prove the handoff.
Figure 1. Valles Marineris east of Tharsis. Image: NASA / MOLA context.
The ordinary view
The usual reading ties the trough to the load of Tharsis: the bulge flexed the crust and the canyon opened as a rift, later widened by collapse and landslides. Yin and others have also read strike-slip. Nothing below voids those papers. The comparison here is only scale and factory.
What was measured
| Valles Marineris | Mariana Trench | |
|---|---|---|
| Length | ~4,000 km | ~2,550 km |
| Typical width | ~200 km (locally to ~600) | ~69 km |
| Maximum depth | ~7 km usual; up to ~10 km | ~10.94 km (Challenger Deep) |
| Share of the world’s girth | ~19% of Mars | ~6% of Earth |
| What it is | Rift east of Tharsis | Subduction trench |
| Ratio | Valles | Mariana |
|---|---|---|
| Depth / length (at 7 km for Valles) | 1 in 570 | 1 in 233 |
| Depth / length (at 10 km for Valles) | 1 in 400 | 1 in 233 |
| Depth / planetary radius | ~0.21% | ~0.17% |
| Earth feature | Why it is closer than Mariana | Why it is still not Valles |
|---|---|---|
| East African Rift / Afar | Crack beside a plume swell | Usually 1–2 km deep; a family of rifts |
| Dead Sea Transform | Strike-slip and pull-apart basins | ~1,000 km; a fault zone, not a canyon |
| Baikal Rift | Deepest open continental rift | Hundreds of km, not thousands |
| Red Sea / Gulf of Aden | A rift after it goes to ocean | Already a young sea, not an open land trough |
Table 3. Earth’s nearer cousins are rifts beside swells. Mariana is the wrong factory.
What would move a clock
| Row | What would move it | What would not |
|---|---|---|
| Rift beside Tharsis | Mostly collapse and erosion, little tectonic opening | A new name for the same trough |
| Depth-to-radius coincidence | A new map that puts maximum depth near 3 km | Choosing 7 km vs 10 km inside the same trough |
| Not a trench | Mariana-style subduction along Valles | East Africa remaining the closer living cousin |
On this reading
This site reads Mars as the last window before living Earth. A lid that does not walk can keep a volcanic load the size of a small continent. A crack of this length next to that load is what that lid does. Earth later adds ocean floor and moving plates. Some rifts become edges. That is lid behaviour.
What would weaken this
If Valles is shown to be mostly collapse and erosion with little tectonic opening, the rift analog shrinks. If a new map puts maximum depth near 3 kilometres, the depth-to-radius coincidence with Mariana goes away. If Mariana-style subduction is demonstrated along the trough, the factory changes. Neither result would prove a handoff.
What this page holds
Valles is longer and wider. Mariana is deeper and steeper. As a fraction of each planet they are close. One is a rift beside Tharsis. The other is a slab going down. This site reads that as lid behaviour on consecutive stages. The missions do not prove the handoff.
Sources
NASA Science; ESA Mars Express. Valles dimensions and the Tharsis-adjacent rift reading.
Challenger Deep compilations (GEBCO; 2021 acoustic/pressure). Mariana length ~2,550 km; depth ~10,935 m.
Yin, A. (2012). Strike-slip reading of Valles compared with the Dead Sea fault system.