Oral presentations and abstracts

The European-Japanese joint mission BepiColombo (ESA/JAXA) will arrive to Mercury on December 2025 after an interplanetary trajectory in which it will perform two flybys of Venus on 15 October 2020 and 11 August 2021. The flybys will be a unique opportunity to study Venus from a multiple perspective. In fact, during the flybys BepiColombo will make Venus observations and measurements in coordination with the Japanese Akatsuki mission, currently in an equatorial orbit around the planet. In addition, a large ground-based campaign to observe Venus has been organized not only during the flyby, but also in August 2020, when Venus reaches its maximum elongation (45º), with an apparent size from Earth of 23-24 arcsec.

Because Venus has a dynamic atmosphere subject to the development of large-scale waves, small scale changes in its winds, and different cloud patterns, and because the views from BepiColombo and Akatsuki are obtained at different phase angles than those observed from Earth, context observations provided by amateur astronomers can significantly enhance the scientific return of the BepiColombo flyby. At the time of this writing (June 2020), we are organizing an additional ground-based amateur campaign to observe Venus during July-October 2020 to support the first Venus flyby. Observations in July will also be used to support the analysis of data acquired during the 3^rd flyby of Venus by the Parker Solar Probe on 11 July 2020.

Amateur observations of Venus are regularly posted in the ALPO-Japan webpages (http://alpo-j.sakura.ne.jp/indexE.htm) and in the PVOL database of amateur observations (http://pvol.ehu.eus) and highlights will be posted in the BepiColombo ESA page dedicated to the flyby (https://www.cosmos.esa.int/web/bepicolombo-flyby/venus1flyby).

The campaign has two roads of collaborations. Firstly, we are encouraging amateur observers to observe Venus in July-October with a particular focus on observations at the end of August and in the week of the flyby. Secondly, we encourage amateur observers to apply for observations in the Europlanet Telescope Network (https://bit.ly/2Br5LDt), where observations of solar system targets and ground-based support of space missions are primary themes. The Telescope Network opened its call for observations on 1 June 2020 and it is open to applications from both professional and amateur astronomers. All applications are reviewed by a scientific board. If granted, the Europlanet Telescope Network will support travel, per diem costs, and local accommodation costs of up to two observers, as well as the incurred service costs of the telescope facilities. The network is also open to non-European participants.

Figure 1 summarizes the viewing geometry of Venus during July – October 2020. Amateur observations of the Venus surface are possible in July and August, and observations of the upper clouds in UV and near-infrared wavelengths are possible through July to October.

Figure 2 shows the trajectories of the BepiColombo and Akatsuki missions close to the Venus flyby. These different perspectives result in different geometries of the observations during the flyby as showed in Figure 3.

The Science potential of an Amateur Campaign

We have issued an observational alert and campaign through PVOL with communication of the amateur campaign using social networks such as Facebook amateur astronomy webpages and email lists such as ALPO, hstJupiter and others. The current campaign has been inspired by the excellent observations of Venus obtained during Spring 2020, and the successful scientific use of Venus amateur observations prior to the Akatsuki orbit insertion in 2015 [1] and during the Messenger flyby of Venus in 2007 [2]. Current studies of Venus atmosphere from Akatsuki also show the potential of amateur observations that complement data obtained by large telescopes or from dedicated spacecraft [3]. In this presentation we will show preliminary results of the observations obtained during July-August, perspectives for the closest approach on October 15 and further plans for a similar campaign during the second BepiColombo flyby of Venus in August 2021.

Updated information on the amateur campaign will be available on the PVOL website at: http://pvol2.ehu.es/bc/Venus/

Acknowledgements

Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149. Y.J. Lee has received funding from the European’s Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 841432. We are very grateful to the ensemble of amateur astronomers sending their data to PVOL and participating in international observation campaigns.

References

[1] Sánchez-Lavega, A., Peralta, J. et al., Venus cloud morphology and motions from ground-based images at the time of the Akatsuki orbit insertion. Astrophysical Journal Letters, 833, L7 (2016), doi: 10.3847/2041-8205/833/1/L7.

[2] Peralta, J., Lee, Y. J. et al. Venus's Winds and Temperatures during the Messenger's flyby: an approximation to a three-dimensional instantaneous state of the atmosphere. Geophys. Res. Lett., 44, 3907–3915 (2017), doi:10.1002/2017GL072900.

[3] Peralta, J., Navarro, T. et al. A Long-Lived Sharp Disruption on the Lower Clouds of Venus. Geophys. Res. Lett., 47, e2020GL087221 (2020), doi: 10.1029/2020GL087221.

How to cite: Garate-Lopez, I., Hueso, R., Lee, Y. J., Mangano, V., Jessup, K. L., Peralta, J., Sanchez-Lavega, A., Zender, J., Benkhoff, J., Murakami, G., and Scherf, M.: Amateur Ground-based Support of the first BepiColombo flyby of Venus, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-1060, https://doi.org/10.5194/epsc2020-1060, 2020.

Abstract

We present the detection and evolution of a planet-scale Cloud Discontinuity on Venus for the first time from amateur data sensing the middle clouds of Venus during March/April 2020. The Cloud Discontinuity was observed mainly as a long vertical dark streak on the dayside hemisphere of Venus in amateur near-infrared images (NIR). Observations were obtained by small telescopes mainly from Greece and Ukraine. Amateur observations will continue in support of professional  earth-based and spacecraft  observations.

Introduction

The dayside upper clouds of Venus (56.5–70 km above the surface) can be observed in UV wavelengths and they drift to the west with velocities 60 times faster than the planet surface, a phenomenon known as superrotation. Imaging the dayside of Venus in the NIR spectrum (~750-1000nm) reveals the morphology and dynamics of the middle clouds (50.5–56.5 km), while longer certain windows at longer infrared wavelengths allow to sense the lower clouds (47.5–50.5 km) on nightside images. Lower-middle and upper clouds comprise the main cloud deck in the atmosphere of Venus. The middle and lower clouds move slower than the upper ones and they were poorly studied until JAXA’s Akatsuki mission. During the year 2016, Akatsuki revealed the presence of a giant discontinuity propagating on the middle and lower clouds. Mysteriously, this discontinuity (interpreted to be a new atmospheric wave), has not been observed on the middle clouds since December 2016.

Methodology

This preliminary analysis is based on measurements on the first available dayside images by authors, 3 by EK and 2 by YN, made in 5-day steps (the period needed for the same feature of middle atmosphere to be visible again) from 11 March  to 31 March 2020. At that epoch (~21/3/2020) Venus presented solar elongation of 46°East, 23 arcsec in diameter, and 52% of illuminated disk. The amateur technique is based on the “lucky imaging” technique combined with special processing to increase contrast. The application WinJupos, was used for feature measurements and analysis.

Analysis

During March 2020, we detected and followed the re-apparition of the Cloud Discontinuity (hereafter CD). It was observed mainly as a long vertical dark streak on the dayside hemisphere of Venus (see Figure 1).

Figure 1: The first image  of the March Cloud Discontinuity. It can be seen as dark vertical streak in the centre of the illuminated disc in the right image (E.Kardasis 11/3/2020 16:45-55 UT, 355mm SCT,ZWO 290MM, Right image 884-900 nm & left image UVenus filter, Glyfada-Athens, Greece)

On the 11th of March EK captured a long dark vertical feature (followed by a brighter streak), suspected to be a CD. We confirmed that it still existed 10 days later when the specific longitude was again observable. An alert was sent to worldwide observers. Previous observations presented not obvious signs of the event. The CD was observed until April 25^th.

The CD spanned between ~30° S and ~30° N, with a total length ranging from ~4500-6500 km and 350-700km width. The CD drifted to the west at an approximate rate of -69° per day.  Speed measurements were made between pair of images (March 11 & 16, March 16 & 21, March 21 & 26) separated by 5-day period. The average speed calculated with the three combination of images confirms that the CD seems to propagate with the same speed during March. The velocity gradually peaks at the equator, reaching ~84 ± 0,5 m/s. When comparing the CD speed with wind speeds of the middle clouds from past reports, we observe that the CD propagates faster than the the average zonal speed of the middle clouds. Finally, we report that the CD is not visible in simultaneous UV images of the upper clouds, confirming previous findings from Akatsuki.

 Acknowledgements

We acknowledge the contribution of ALPO-Japan database, Grischa Hahn for providing support on WinJupos, and Iakovos-Marios Strikis for the technical support. 

How to cite: Kardasis, E., Peralta, J., Maravelias, G., and Naryzhniy, Y.: Amateur observations of a planetary-scale wave in the middle clouds of Venus , Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-712, https://doi.org/10.5194/epsc2020-712, 2020.

Introduction

Many of Juno’s observations use external information to determine their context in space and time for the “snapshots” of usually very limited regions of the planet that it detects in its close approaches (“perijoves”, PJs).  This has been the role of the campaign of supporting observations from the professional community, but it has always been bolstered by the near-continuous observations made by the increasingly sophisticated cadre of the world-wide amateur network.  This year is one in which this role was particularly apparent.

Tracking Activity in Jupiter

Among the many areas of interest in Jupiter undergoing changes are the following.

   Great Red Spot (GRS).  Continuing activity follows on from remarkable interaction of small-scale anticyclones transported counter-clockwise inside the GRS Hollow throughout the spring and fall of 2019. These caused arcuate features, commonly called “flakes”, to appear on the western side of the GRS , which were likely to be material swept off the upper portions of the GRS itself [1]. JunoCam continued to record evidence of them during geocentric solar conjunction at PJ23, PJ24 & PJ25, and  the amateur community has continued to monitor them in early 2020.  We expect that this type of interaction will continue, as it is apparently tied to the secular longitudinal shrinkage of the GRS, with the results distinguishing between different models for the dynamical interactions involved [2,3].

   Equatorial Zone Disturbance.  The Equatorial Zone (EZ) was predicted to undergo a disturbance based on the cyclic nature of past events [4] with a major disruption of its bright visual and cold 5-µm appearance.  Although the disruption of its 5-µm appearance did not happen, the EZ darkened in blue and UV light, and there was an increase in the thickness or altitude of an upper-atmospheric haze [5]. The amateur-observation record shows that a darker shade of its visual appearance is still present as this coloration episode declines.  Juno scientists continue to be interested in the EZ to determine whether such events relate to changes in the remarkably deep-seated upwelling of air detected by the Juno Microwave Radiometer as a column of concentrated ammonia gas [6].  So we are interested in changes to the color, either a return to its normally bright appearance or a renewed darkening that might presage a true disruptive event that is simply “late”.

  Outbursts.  Two major outbursts of convective plumes were observed by JunoCam, one in the North Temperate Belt shortly before PJ2 [7] and another in the South Equatorial Belt near PJ4 [8,9] that was associated with lightning detections [10].  Such outbursts are of interest to Juno scientists. Hi-res amateur imaging also synergizes with JunoCam in characterizing smaller outbursts.  One notable example, discovered just before this writing by Foster [11], was recorded in detail by JunoCam at PJ27, showing some morphological similarities with the initial development stages of terrestrial tropical storms.

Overcoming COVID-19 Disruptions

For recent Juno orbits, low-latitude regions are observed at extremely oblique angles except during perijoves when off-Earth pointing of the spacecraft is adopted.  These are chosen carefully because they use up fuel that the Juno science team would like to reserve for an extension of the mission. A single orbit in 2020, chosen for such a turn at PJ26 on April 10, turned out to be in the middle of the COVID-19 pandemic when nearly all professional observatories scheduled to provide Juno support were shuttered. Except for two semi-automated observatories and Hubble Space Telescope, whose ground crew were deemed “essential”, it was the amateur community who provided the only information about Jovian variability during this time.   This was also true for PJ27 on June 2, when a few more professional observatories opened.

Future Prospects

We hope for continued support from the amateur community. Scientists on the Juno mission hope to persuade NASA to fund an extension; one candidate scenario could extend out to PJ70 in late 2025.  This would not only extend the time line for continued observations of atmospheric evolution but would take advantage of different types of observations not possible during the primary mission, due to orbital geometry.  We would hope observations by this community would continue to provide the continuity of atmospheric scrutiny from which we have benefitted so far.

References

[1] Foster et al. 2020.  The Great Red Spot in 2019 and its interaction with retrograding vortices as monitored by the amateur planetary imaging community. https://britastro.org/node/22552

[2] Sanchez-Lavega, et al. 2019. Jupiter’s Great Red spot threatened along 2019 by strong interactions with close anticyclones. Amer. Geophys. Union meeting. P44A-01.

[3] Marcus, et al. 2019. On the shedding of flakes by Jupiter’s Great Red Spot: It is not dying. Amer. Geophys. Union meeting. P13B-3505.

[4] Antuñano, et al. 2018.   Infrared characterisation of Jupiter's equatorial disturbance cycle.  Geophys. Res. Lett.  45, 10987-10995.

[5] Orton, et al. 2019. Juno and Juno-supporting observations of Jupiter’s 2018-2019 Equatorial Zone disturbance. EPSC-DPS2019-109.

[6] Li et al. 2017. The distribution of ammonia on Jupiter from a preliminary inversion of Juno microwave radiometer data. Geophys. Res. Lett. 44, 5317-5325.

[7] Sanchez-Lavega et al. 2017. A planetary-scale disturbance in the most intense Jovian atmospheric jet from JunoCam and ground-based observations. Geophys. Research Lett.  44, 4679-4686.

[8] de Pater et al. 2019. First ALMA millimeter wavelength maps of Jupiter, with a multi-wavelength study of convection. Astronomical Journal. 158, 139 (17pp).

[9] Wong, et al. 2020. High-resolution UV/optical/IR imaging of Jupiter in 2016-2019. Astrophys. J. Suppl. Ser. M. H. Wong, et al. 2020. High-resolution UV/optical/IR imaging of Jupiter in 2016-2019. Astrophys. J. Suppl. Ser. 247:58 (25 pp).

[10] Brown et al. 2018. First detection of lightning sferics from Jupiter reveals new insights into the global distribution of moist convection.  Nature 558, 87-90.

[11] Foster et al. 2020. A rare methane-bright outbreak in Jupiter’s South Temperate domain.  EPSC2020.

How to cite: Orton, G., Momary, T., and Rogers, J.: The Role of Amateur Astronomers in Documenting the Spatial Context and Time Evolution of the Jovian Atmosphere to Benefit the Juno Mission, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-174, https://doi.org/10.5194/epsc2020-174, 2020.

Introduction

The Juno mission has given the first opportunity to characterise the flow patterns in Jupiter’s south polar region (SPR). Fast winds can be measured by comparing hi-res JunoCam images over up to 2 hours within a single pass, which shows in detail the motion of the southernmost jet at 64ºS (all latitudes planetocentric), and the circulations of cyclonic folded filamentary regions (FFRs) and anticyclonic white ovals (AWOs) further south [1]. However, Juno data cannot trace slower motions, in particular the drifts of these coherent circulations over days to months.  Over the 53-day interval between perijoves a few AWOs can be recognised, but the interval is too long to recognise individual FFRs, which are the dominant structures of this region.  The best amateur ground-based images now have sufficient resolution to identify and track some of these features.  Here, we use maps and measurements from amateur images in 2016-2020, combined with JunoCam maps that provide secure identification of the features. Thus we find that pale patches in ground-based images usually represent FFRs in Juno maps, and some small light spots are AWOs.  

Measurements of drifts of FFRs over days (e.g. Fig.1)

From hi-res images by several amateur observers, we made south polar projection maps using WinJUPOS [2].  From blinking and animating these maps, we find that features in the SPR could only be tracked using v-hi-res images at intervals of less than 5 days; FFRs cannot be confidently identified over longer gaps as they change shape and position rapidly, although they may last for weeks. With maps spaced by 2-4 days, it is possible to observe their zonal motions and changes in outline. This is best done within a few days of a Juno perijove so that the features can be identified in the Juno map. 

We selected several short series of maps in 2018 April-May and 2020 April-June that gave the clearest results, mostly using I-band images by A.C. as these were most consistent.  Preliminary results show:

--Features at ~60-65ºS are prograding (around the S6 jet at 64ºS).

--Features at ~66-74ºS are retrograding (including FFRs in the belt), with speeds comparable to those of the AWOs (see below).

-- Around 66ºS, where JunoCam images often show FFRs in the belt apparently extending north towards the S6 jet, they can sometimes be observed being sheared accordingly, with the north part of the FFR prograding close to the jet (e.g. Fig.1).

Measurements of drifts of AWOs at ~70-74ºS over weeks to months

The JunoCam maps (e.g. Fig.1) show several AWOs in this latitude range at every perijove.  We have tracked these white ovals from 2016 to 2018 using positions from JunoCam (our maps) and ground-based images (measurements and maps by the JUPOS team) plus a few from HST (OPAL maps).  Fig.2 shows part of the chart.

The largest AWO (A) has been tracked from 2015 (pre-Juno) to 2020.  Some other ovals have probably existed for at least 8 months each, regardless of latitude, although small ones cannot always be tracked between perijoves. Some ovals have merged or disappeared within the first two years of the Juno coverage. Others are seen passing each other in different latitudes in Juno maps, although we cannot tell which is which thereafter. There are also even smaller AWOs and eddies, so there may be rapid turnover by growth, wandering in latitude, and mergers or disappearance.

The resulting zonal drift profile (ZDP) is in Fig.3.  These AWOs move with essentially uniform retrograde flow from 69.5-72.4ºS, [in L3, +42 (±3) deg/53d, -3.8 to -3.2 (±0.25) m/s], but at higher latitudes, above 72.4ºS, they show a steep gradient to faster (prograding) speeds.  The highest-latitude and fastest speeds (spots P & E’: Fig.3) are close to those of small AWOs that drift irregularly around the periphery of the south polar pentagon of cyclones at ~80ºS [3].  There we found one shift of -44 deg in 53d, and several of ~-29 deg in 53d.

Conclusions

The main belt of FFRs is retrograding, along with the AWOs on its S edge.  On its N edge, disturbance from FFRs often extends north to the S6 jet and is entrained by the prograding jet.

The ZDP (Fig.3) resembles that of high-latitude northern domains (N4, N5)[4], so the belt of FFRs and the loose ring of AWOs just south of it partially retain the organised structure of regular domains, although unconfined towards the pole.

South of 73ºS, long-term zonal drifts of AWOs become prograding with a steep gradient of mean speed increasing towards higher latitudes, where it becomes comparable to drifts of AWOs around the polar pentagon.

A companion abstract in the OPS1 session [1] describes the short-term wind measurements derived from the JunoCam maps at individual perijoves.

References

Figure 1.  Examples of maps used for tracking FFRs in 2018.

Figure 2.  Excerpt from chart tracking AWOs.  (L2 moves at +8.0º/30d relative to L3.)

Figure 3.

How to cite: Rogers, J., Casely, A., Adamoli, G., Jacquesson, M., Vedovato, M., Bullen, R., Mettig, H.-J., Eichstädt, G., Hansen, C., Orton, G., and Momary, T.: Jupiter’s south polar region (~60-75ºS): Medium-term flow patterns from amateur and JunoCam maps, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-153, https://doi.org/10.5194/epsc2020-153, 2020.

Introduction

Energetic, high altitude eruptions in Jupiter’s atmosphere, which we refer to as outbreaks, are not uncommon in the North and South Equatorial Belts (NEB and SEB) as well as higher latitudes. However, few have been observed in the Temperate regions. An intense methane-bright outbreak in the South Temperate Belt (STB) latitudes was observed by the lead author on 2020 May 31. Although the outbreak, which would become known as “Clyde’s Spot” in the Pro-Am planetary community, faded quite rapidly in methane wavelengths, developments were monitored by the amateur community over the following weeks. The outbreak occurred two days prior to the Juno Perijove 27 flyby, and close Pro-Am collaboration resulted in very high-resolution images of the outbreak being obtained by the JunoCam imager during the flyby.

Outbreak detection

The outbreak occurred in the southern part of a pre-existing small white spot at 31⁰S, embedded in a pale grey streak, and suspected of being a cyclonic vortex and was detected early on the 31 May.  Observations from other amateurs confirmed that the outbreak had occurred within the previous 10 hours.  It was only slightly brighter than before in RGB, but extremely bright in the 0.89 micron CH4 absorption band.  It remained methane-bright though much weaker over the following rotations, and from June 1 onwards appeared to consist of two (individually unresolved) parts which moved gradually apart up to June 6, mostly in the E-W direction but with slight cyclonic rotation from June 1-3.

NASA Juno PJ27

The JunoCam images on June 2 showed Clyde’s spot as an unusual, roughly oval, bright spot in RGB and CH4, with brighter arcs in its E and W ends that were the pair of methane-bright spots in ground-based images.  The spot does not show popup clouds but is marked by numerous concentric arcs which could represent gravity waves in the expanding high-level white cloud (A. Casely). Surrounding streaks confirm that it is within a strongly cyclonic vortex, although it may be over-riding those streaks on the S side.

Outcome of the outbreak

Amateur images from June 2-3, only small spots at the site of the initial eruption.  From June 3 to June 13, v-hi-res images showed at least one white spot and one very dark spot; they changed rapidly in detail, possibly with cyclonic motion.  No obvious changes have developed outside this site, apart from appearance of thin blue-grey lines close to the STBn and STBs jets for ~13 deg west Clyde’s spot.  In methane images, by June 11 the appearance had reverted to a short oblique methane-dark streak with no bright spot, as it was before the eruption.

Cycles of STB Structured sectors

This spot erupted tens of degrees east of the only large anticyclonic oval in this domain, Oval BA.  Small cyclonic spots have repeatedly arisen here in the last 20 years and expand to form structured sectors of the STB, which persist as large cyclonic segments for several years until they catch up with Oval BA from the west side.  Although a new structured sector has been anticipated, it was only ground-based images early in 2020 that showed two new features which could be its precursors.  One was a small, very dark spot ~40⁰ east of BA, which persists; the other was the faint oblique streak, centred on a tiny white spot, ~80⁰ east of BA.  Clyde’s spot erupted in this latter white spot.  Therefore, this eruption may be a previously unknown feature of a cyclonic vortex in this transitional location and stage. Although the outbreak was very short-lived, implying similar outbreaks might be occurring unobserved, its occurrence in this location suggests that it was significant.

The outbreak in the context of previous outbreaks.

The only similar methane-bright outbreaks previously recorded in the cyclonic STB latitudes were in large structured sectors at the end of their life: the so-called STB Remnant in 2010 and the STB Ghost in 2018 [1,2].  These generated rapidly expanding disturbances that converted these long cyclonic circulations into dark turbulent STB segments.  In contrast, Clyde’s spot, being in a very compact cyclonic vortex, has remained confined in its immediate vicinity and has not developed further (as of 2020 June 22). 

Similar plume outbreaks occasionally occur in small but stable cyclonic vortices in the SEB. This was the way in which at least two recent SEB Revivals [2007, 2010] and two mid-SEB outbreaks [1979, 2017] began, and it is possible that they always do so. 

Conclusion

This was a single, very energetic plume eruption within the small cyclonic spot. Over the following days the plume expanded locally, and disturbance continued at the original site, but there is no evidence of substantial wider changes.  This contrasts with the results of the similar eruptions within larger circulations, which were rapidly converted into turbulent dark STB segments. Clyde’s spot was a brief event, never conspicuous in visible light, but detected because of frequent monitoring with methane images. It may represent a previously unknown type of eruption in a small cyclonic spot in the early stages of development of a STB structured sector. An update will be provided in the presentation.

Figures:

‘Clyde’s spot’ in 889 nm methane band (left) and RGB (right): (Top) initial detection from C.F. on 31 May 2020; (Bottom) closeups from JunoCam on 2 June 2020.