Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 18: North-west flank of Arsia Mons

Strong · roughly 85%

Two CTX close-ups of the same 600 by 600 m on the flank of Arsia Mons, from September 2008 and July 2025, under a similar sun. Three or four small dark dots near the arrow are present only in the 2025 image. — The same 600 × 600 m in September 2008 and July 2025, under a similar sun. The arrow marks the new dots. NASA/JPL-Caltech/MSSS.

What changed. Three or four dark dots, each 15 to 30 m across and spread over about 150 m, appeared on the north-west flank of the volcano Arsia Mons between December 2016 and January 2025. They keep the same pattern in two later images, from May and July 2025.

Why it may be a new impact. Seven earlier images, from 2008 to 2016, show no dots there, and each of them would have shown them. A tight cluster of small dark spots is the classic mark of a meteoroid that broke up in the air before hitting the ground, and dark patches made by wind are not clusters of separate dots.

Location: 5.277° S, 237.518° E (122.482° W)
Absent: seven images from 15 August 2008 to 3 December 2016
Present: 23 January 2025, 25 May 2025 and 14 July 2025
Size: Three or four dark dots, each 15 to 30 m across, spread over about 150 m
Confidence: Strong candidate; roughly 85% that it is a new impact.
Nearby: Candidate 24, 75 km to the north-north-west, first shows in the same image of 23 January 2025. They are separate impacts: the craters of one broken-up meteoroid lie at most a few kilometres apart.
Caveat: It has been followed for only six months, so a short-lived dark patch made by wind is not excluded, although such patches are not clusters of separate dots. It lies outside every footprint of the high-resolution HiRISE camera. Like every candidate here, it is unconfirmed: see the caveat.

Ten CTX images of the same 2 by 2 km patch, from 2007 to 2025; the first is featureless and some have black areas without data. Three or four small dark dots near the arrow are absent up to 2016 and present in the three images from 2025. — Ten of the eleven CTX images of the same 2 × 2 km patch, 2007 to 2025. The July 2007 image, taken during a dust storm, shows no surface detail, and black areas have no data. The dots appear in January 2025. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from July 2025 of the volcano’s flank around the dots, with a dashed box around the 2 by 2 km patch and an arrow at the dots. — A 12 × 12 km view from July 2025. The dashed box is the 2 × 2 km patch. NASA/JPL-Caltech/MSSS.

The independent check: three columns of the same ground, 2 km wide above and 600 m wide below, with yellow ticks around the dots. The dots are missing in the earlier image, 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 dots would have been visible had they been there; those marked AFTER show them. Each image keeps one contrast stretch in both rows, so the close-up cannot create a spot. NASA/JPL-Caltech/MSSS.