2025 June 1

Mars Opposition Blog 1 June 2025

Richard Mckim

1st June 2025

The planet is now remote, well under 6 arcseconds in diameter, and observable only in the evening twilight. However, daily coverage continues by those sufficiently equipped to do so (and not having awkwardly-placed trees or buildings).

No changes in albedo features have been seen. The planet continues to show the usual seasonal behaviour. Dust activity has not been detected since the last blog entry.

The north polar cap is now very small. A very recent image by Nick Haigh (May 28) shows a seasonal rift in the N. polar cap (with a possible brighter patch on the following side). It also shows the continuing equatorial cloud belt, and the summits of Olympus Mons and the Tharsis Montes poking through the extensive white morning cloud. Another view by Clyde Foster (May 26) shows similar effects. The exceptionally dark patch near the cap in these images is Hyperboreus Lacus, a feature of this time of the martian year.

The equatorial cloud belt continues to cause a bluish or greenish tint to the Syrtis Major, especially when near the edge of the disk, and this effect was again reported by Frank Melillo on May 18 and 20. In blue light the Syrtis is invisible even at the CM. David Basey had a similar view on May 15, while Paul Abel observing visually on May 12 caught the bluish tint over the morning Syrtis.

The frost at Hellas mentioned in the last blog entry continues to be visible, and it was confirmed visually by Abel, Stanislas Macsymowicz, Andy Wilson and the Director. Here is an image by Mark Lonsdale (May 25) that shows it, and also confirms that the Olympia region had become seasonally detached from the N. polar cap.

Evening cloud over Olympus Mons and Tharsis Montes continued to be visible. For example, Peter Tickner caught the Olympus Mons cloud near the evening limb on May 19. On the 16th he imaged some light afternoon cloud over Elysium too. And here is an image by Martin Lewis (May 22) which in addition to showing orographic clouds, portrays the small dark dot of Propontis clearly on the NE side of Elysium, following the CM. His image also shows the detached Olympia.

I have received further images of the terminator projection mentioned in an earlier blog post, from Nick Haigh, who caught it on February 27/28.

All observations are welcome, and will continue to be acknowledged. If enough data are received, this blog will continue. We may not be able to record as much detail now, but we wish to monitor as much of the current martian year as we possibly can in order to time the various expected phenomena. By the start of August, the planet’s declination will soon favour the southern hemisphere, but I hope that UK observers can continue for at least a little into June.