2025 July 24

Mars Opposition Blog 24 July 2025

Richard McKim

2025 July 24

Mars continues to receive attention. The disk diameter, as of July 30, will be a mere 4.4 arcseconds.

The next significant event of the martian year ought to be the fairly brief appearance of the cyclonic or spiral clouds near the N. polar cap. These were described in some detail in our reports of similar oppositions from the 2010s. See Part 2 of each of our reports for 2012, 2014 and 2016 (posted at the Section website). The clouds, which sometimes reveal their circular nature by virtue of a darker centre, are to be found primarily upon the morning side of the disk at the longitudes of Baltia/Mare Boreum and Utopia. The initial values of Ls for when they appear vary slightly. In 2012, 2014 and 2016 they commenced at Ls = 116, 117 and 126, respectively, sometimes appearing at the start as curved wisps rather than complete circles. Their spiral nature may not show up until around Ls = 126.

On July 30, Ls will reach 118 degrees, so these phenomena could be visible by then. Will any observer be able to catch them?

Paul Abel recently made a pleasing apparition map from his visual work, and I am posting it here. I have also received summary maps comparing 2018, 2020, 2022 and 2025 from Mark Lonsdale.

Posted here are representative recent images by Foster (Namibia), Lewis (UK), Lonsdale (Australia), Melillo (USA), and Ito, Kurisu & Watanabe (the latter all from Japan). Comments made in my last blog post about the Hellas frost, equatorial cloud belt and orographic clouds apply equally to these.

The front page contributor list has once again been updated, and we now have a very respectable total of 111 observers.