Professor of Mathematics

Paata Ivanisvili

Department of Mathematics, University of California, Irvine

Candidate 37: Rippled lava plains south-west of Biblis Tholus

Strong · roughly 80%

Two CTX close-ups of the same 500 by 500 m of wind-rippled plains south-west of Biblis Tholus, from May 2012 and April 2025, under the same sun. A small dark spot at the arrow is present only in the 2025 image. — The same 500 × 500 m in May 2012 and April 2025, under the same sun. The arrow marks the new spot. NASA/JPL-Caltech/MSSS.

What changed. A small dark spot 25 to 40 m across appeared on wind-rippled lava plains south-west of the volcano Biblis Tholus, between May 2012 and July 2023. It is still there in April 2025.

Why it may be a new impact. A May 2012 image, taken under the same sun and lined up almost perfectly, would have shown it clearly and shows plain ground. The spot is round, spans several ripple crests and has not moved or changed shape in 21 months, so it is not a shadow or drifting sand.

Location: 0.683° S, 234.028° E (125.972° W)
Absent: 30 May 2012
Present: 14 July 2023 and 21 April 2025
Size: Small dark spot 25 to 40 m across
Confidence: Strong candidate; roughly 80% that it is a new impact.
Caveat: Dark sand gathering in the ripple troughs is the main alternative, and the spot is small and only moderately dark, so the confidence is lower until a HiRISE image is taken. It lies outside every footprint of the high-resolution HiRISE camera. Like every candidate here, it is unconfirmed: see the caveat.

Four CTX images of the same 2 by 2 km patch of rippled plains, from 2011 to 2025; the first is featureless. A small dark spot at the arrow is absent in 2012 and present in 2023 and 2025. — All four CTX images of the same 2 × 2 km patch, 2011 to 2025. The April 2011 image shows no surface detail at the spot. NASA/JPL-Caltech/MSSS.

A 12 by 12 km CTX view from April 2025 of the rippled 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.