Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 36: Plains on the west rim of Echus Chasma

Strong · roughly 90%

Two CTX close-ups of the same 500 by 500 m of smooth plains west of Echus Chasma, from July 2016 and February 2025, under a similar sun. A very dark spot at the arrow is present only in the 2025 image. — The same 500 × 500 m in July 2016 and February 2025, under a similar sun. The arrow marks the new spot. NASA/JPL-Caltech/MSSS.

What changed. A compact, very dark spot about 60 by 50 m appeared on smooth plains about 2 km west of the rim of Echus Chasma, between July 2016 and March 2023. It is still there, a little fainter, in February 2025.

Why it may be a new impact. Images from 2006, 2012 and 2016 show plain ground there, and each of them would have shown a spot this dark. The two images that show it were taken under the same sun, so the fading is real, and a dark spot that appears on level ground and then slowly fades behaves like the blast zone of a fresh impact. Dark slope streaks are common on the chasma’s wall, but this spot is on flat plains.

Location: 2.524° N, 278.779° E (81.221° W)
Absent: 22 December 2006, 12 October 2012 and 25 July 2016
Present: 29 March 2023 and 12 February 2025
Size: Compact, very dark spot about 60 × 50 m
Confidence: Strong candidate; roughly 90% that it is a new impact.
Nearby: Candidate 29, 91 km to the north, first shows in the same image of 29 March 2023, and candidate 32 is 296 km away. All three are near Echus Chasma, but they are separate events: no single meteoroid scatters craters that far apart.
Caveat: It lies outside every footprint of the high-resolution HiRISE camera; the nearest ends 3.2 km away. Like every candidate here, it is unconfirmed: see the caveat.

Five CTX images of the same 2 by 2 km patch, from 2006 to 2025. A very dark spot at the arrow is absent in 2006, 2012 and 2016 and present in 2023 and 2025. — All five CTX images of the same 2 × 2 km patch, 2006 to 2025. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from February 2025 of the plains beside Echus Chasma, with a dashed box around the 2 by 2 km patch and an arrow at the spot. — A 12 × 12 km view from February 2025. The dashed box is the 2 × 2 km patch. NASA/JPL-Caltech/MSSS.

The independent check: four columns of the same ground, 2 km wide above and 600 m wide below, with yellow ticks around the spot. The spot is missing in the two earlier images, marked BEFORE, and present in the two later images, marked AFTER. — **Independent check.** A second, deliberately sceptical review downloaded every image again and found that the candidate passes every test. Each column is the same ground, north up, 2 km wide above and 600 m wide below. Columns marked BEFORE are earlier images in which the spot would have been visible had it been there; those marked AFTER show it. Each image keeps one contrast stretch in both rows, so the close-up cannot create a spot. NASA/JPL-Caltech/MSSS.