Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 23: Northern Arabia Terra, north-west of Cassini crater

Strong · roughly 85%

Two CTX close-ups of the same 800 by 800 m north-west of Cassini crater, from September 2008 and May 2025, under a similar sun. A round dark spot at the arrow is present only in the 2025 image. — The same 800 × 800 m in September 2008 and May 2025, under a similar sun. The arrow marks the new spot. NASA/JPL-Caltech/MSSS.

What changed. A dark spot about 150 m across, with a darker core about 90 m across, appeared north-west of Cassini crater between September 2018 and August 2020. It is unchanged in images from 2022 and 2025.

Why it may be a new impact. Images from 2008, 2014 and September 2018 show nothing there. The 2018 image was taken at the end of a global dust storm, which cut its contrast to about a third, but a spot this dark would still have shown. It is seen with the sun at many heights, so it is not a shadow, and a round spot with a darker core that stays the same for five years is what the blast zone of a small impact looks like.

Location: 29.099° N, 27.066° E
Absent: 25 September 2008, 8 December 2014 and 11 September 2018
Present: 3 August 2020, 17 June 2022, 22 March 2025 and 22 May 2025
Size: Dark spot about 150 m across, with a darker core about 90 m across
Confidence: Strong candidate; roughly 85% that it is a new impact.
Caveat: Every CTX image of it from 2008 to 2022, including the 2020 image in which it first shows, was taken while HiRISE was monitoring an older impact 9.7 km away, so the camera teams may know of it without having published it. No HiRISE image covers it; the nearest ends 4.9 km away. Like every candidate here, it is unconfirmed: see the caveat.

Eight CTX images of the same 2 by 2 km patch, from 2008 to 2025; the second shows other ground. A round dark spot is absent up to 2018 and present from 2020 on. — Eight CTX images of the same 2 × 2 km patch, 2008 to 2025. The August 2010 image does not cover the spot (its panel shows other ground), and in the March 2025 panel the alignment slipped, so the spot lies below and to the left of the arrow. The spot first appears in August 2020. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from May 2025 of the ground north-west of Cassini crater, with a dashed box around the 2 by 2 km patch and an arrow at the spot. — A 12 × 12 km view from May 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.