Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 25: Elysium Planitia, about 540 km east of the InSight lander

Strong · roughly 90%

Two CTX close-ups of the same 600 by 600 m of Elysium Planitia, from September 2023 and April 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 September 2023 and April 2025, under a similar sun. The arrow marks the new spot. NASA/JPL-Caltech/MSSS.

What changed. A compact dark spot about 55 by 75 m appeared on the plains of Elysium Planitia between 6 September and 25 December 2023, a window of under four months. It is still there in April 2025.

Why it may be a new impact. Four earlier images, from 2012 to September 2023, show nothing there under similar suns, and each of them would have shown it. A compact dark spot that appears within weeks and then stays unchanged for 16 months is the typical mark of a new impact, not of a shadow or a short-lived patch made by wind.

Location: 7.497° N, 144.313° E
Absent: 3 June 2012, 3 May 2020, 7 December 2021 and 6 September 2023
Present: 25 December 2023 and 25 April 2025
Size: Compact dark spot about 55 × 75 m
Confidence: Strong candidate; roughly 90% that it is a new impact.
Caveat: It lies in the area of a catalogue of new impacts near the InSight lander (Bickel et al. 2025) that could not be downloaded, but it formed after the period that catalogue covers. It lies outside every footprint of the high-resolution HiRISE camera. Like every candidate here, it is unconfirmed: see the caveat.

Six CTX images of the same 2 by 2 km patch, from 2012 to 2025. A compact dark spot at the arrow is absent in the four images up to September 2023 and present in December 2023 and April 2025. — All six CTX images of the same 2 × 2 km patch, 2012 to 2025. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from April 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 April 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.