Jupiter in 2025/26, Report no.2

John Rogers (2025 Oct.14)

This is a brief report on the  present state of the planet.  Figure 1 is a map from 2025 Oct.1-3 with long-lived anticyclonic ovals and several other features labelled.

North Temperate Belt (NTB):  Following last year’s spectacular NTBs jet outbreak, the NTB is fully revived, with grey-brown shading throughout the NTB(N) and NTZ (separated by an irregular wavy bright line), while the NTB(S) is orange (though rather pale at some longitudes).  Very few spots can be tracked in the NNTBs jet, suggesting that the NTBs outbreak has suppressed or masked this activity, as usual.

NTBs jet: Several dark spots have been visible on the south edge of the NTB(S), with speeds somewhat slower than the jet peak.  [Further details in attached PDF version]

North Equatorial Belt (NEB):  The NEB broadened in 2023/24, and now has an array of ‘barges’ (dark brown cyclonic spots) and ‘portholes’ (AWOs) as is typical after such events.  The expanded northern part is beginning to recede again.

Equatorial Zone (EZ):  There is still extensive shading over most of the EZ, mostly ‘warm grey’, and mixed with dark bluish-grey streaks in festoons from the NEBs and SED.

South Equatorial Disturbance (SED):  The main complex of the SED has been conspicuous recently (Figure 2). Its very dark bluish portion is exceptional in having a greenish tint (as pointed out by Steve Hill – in contrast to the NEBs dark formations), and being extremely dark in the methane band.

Great Red Spot (GRS):  Measurements of the GRS by Shinji Mizumoto (Figure 3) show that during solar conjunction it has accelerated (from DL2 = +1.8 to +1.2 deg/30d) and expanded slightly (from 11.2° to 11.5° long).  On Sep.1 it was at L2=77, L3=292.

Shinji Mizumoto has also posted a valuable compilation of images and measurements of the GRS throughout its history:  ‘1879-2025 Jupiter’s Great Red Spot by S.Mizumoto’:  https://alpo-j.sakura.ne.jp/kk25/j251006r.htm

South Temperate Belt (STB) & S.S. Temperate Belt (SSTB):  The STB is still a prominent dark belt around most of the planet.  Oval BA is distinctly reddish now. The SSTB, pockmarked by the 7 long-lived AWOs, has reddish sectors and three white oblongs.

A pair of bright outbreaks in STB & SSTB:  Two outbreaks of small white spots have appeared, one in the STB and one nearby in the SSTB, approaching the GRS (Figures 4-6) Each began with a small bright spot, also very bright in the methane band, in pre-existing cyclonic structures.  The first appeared in the STB on Sep.22, in a small red cyclonic oval.  This was similar to the few previous convective outbreaks observed in the STB, but the first one to occur without any apparent triggering factor.  Then a similar outbreak appeared in the SSTB on Oct.4, in a dull white oblong. Their proximity suggests that one might have triggered the other. They have rapidly expanded, and we wait to see if they will develop into persistent chaotic regions (FFRs).  [Further details in attached PDF version]

Satellite phenomena:  There have been some beautiful groupings of the Galilean moons recently, especially when in transit, illustrating the coupling of their orbits (Figures 7-9) (with thanks to the observers, and to ALPO-Japan for some of these images).

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The full text of this report, plus small copies of the figures, is in this PDF:   Report_2025-26_no-2_&Minifigs

The full-size figures are in this ZIP file:  Report-no-2_Figures 

Some of the figures are copied below: