Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 24: Plains north of Arsia Mons, south of Biblis Patera

Strong · roughly 80%

Two CTX close-ups of the same 600 by 600 m of plains north of Arsia Mons, from December 2015 and May 2025, under a similar sun. A compact dark spot at the arrow is present only in the 2025 image. — The same 600 × 600 m in December 2015 and May 2025, under a similar sun. The arrow marks the new spot. NASA/JPL-Caltech/MSSS.

What changed. A compact dark spot about 60 by 45 m appeared on the plains north of Arsia Mons between December 2015 and January 2025. It is in images from January and May 2025, taken on two orbits.

Why it may be a new impact. Three earlier images, from 2008 and 2015, show nothing there, and each of them would have shown it; one of the 2008 images was taken under the same sun, so the spot is not a shadow. A compact new dark spot seen on two orbits is the classic signature of a small fresh impact.

Location: 4.068° S, 237.126° E (122.874° W)
Absent: 15 August 2008, 14 October 2008 and 15 December 2015
Present: 23 January 2025 and 25 May 2025
Size: Compact dark spot about 60 × 45 m
Confidence: Strong candidate; roughly 80% that it is a new impact.
Nearby: Candidate 18, 75 km to the south-south-east, 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 four months, so a short-lived dark patch made by wind is not excluded, although its compact shape argues for an impact. It lies outside every footprint of the high-resolution HiRISE camera. Like every candidate here, it is unconfirmed: see the caveat.

Five CTX images of the same 2 by 2 km patch, from 2008 to 2025. A compact dark spot at the arrow is absent in 2008 and 2015 and present in both 2025 images. — All five CTX images of the same 2 × 2 km patch, 2008 to 2025. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from January 2025 of the plains around the spot, with a dashed box around the 2 by 2 km patch and an arrow at the spot. — A 12 × 12 km view from January 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 spot. The spot is 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 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.