Using archival near-infrared observations from the Keck and Lick Observatories and the Hubble Space Telescope, we document the evolution of Neptune’s cloud activity from 1994 to 2022. We calculate ...the fraction of Neptune’s disk that contained clouds, as well as the average brightness of both cloud features and cloud-free background over the planet’s disk. We observe cloud activity and brightness maxima during 2002 and 2015, and minima during 2007 and 2020, the latter of which is particularly deep. Neptune’s lack of cloud activity in 2020 is characterized by a near-total loss of clouds at mid-latitudes and continued activity at the South Pole. We find that the periodic variations in Neptune’s disk-averaged brightness in the near-infrared H (1.6μm), K (2.1μm), FWCH4P15 (893 nm), F953N (955 nm), FWCH4P15 (965 nm), and F845M (845 nm) bands are dominated by discrete cloud activity, rather than changes in the background haze. The clear positive correlation we find between cloud activity and Solar Lyman-Alpha (121.56 nm) irradiance lends support to the theory that the periodicity in Neptune’s cloud activity results from photochemical cloud/haze production triggered by Solar ultraviolet emissions.
•Neptune’s near-infrared cloud activity from 1994 to 2022 exhibits periodic variation.•We show evidence that Neptune’s cloud activity is correlated with Solar activity.•During late 2019 there was a dramatic drop in Neptune’s cloud activity.•From late 2019 onwards, only the south pole exhibited cloud activity.
Using near-infrared observations of Neptune from the Keck and Lick Observatories, and the Hubble Space Telescope in combination with amateur datasets, we calculated the drift rates of prominent ...infrared-bright cloud features on Neptune between 2018 and 2021. These features had lifespans of ∼1 day to ≥1 month and were located at mid-latitudes and near the south pole. Our observations permitted determination of drift rates via feature tracking. These drift rates were compared to three zonal wind profiles describing Neptune’s atmosphere determined from features tracked in H band (1.6 μm), K’ band (2.1 μm), and Voyager 2 data at visible wavelengths. Features near −70deg measured in the F845M filter (845 nm) were particularly consistent with the K’ wind profile. The southern mid-latitudes hosted multiple features whose lifespans were ≥1 month, providing evidence that these latitudes are a region of high stability in Neptune’s atmosphere. We also used HST F467M (467 nm) data to analyze a dark, circumpolar wave at −60° latitude observed on Neptune since the Voyager 2 era. Its drift rate in recent years (2019–2021) is 4.866±0.009°/day. This is consistent with previous measurements by Karkoschka (2011), which predict a 4.858±0.022°/day drift rate during these years. It also gained a complementary bright band just to the north.
•Late 2019 through 2020 showed a decrease in clouds at mid-latitudes.•The South Pole remained active during 2020 as the primary region of cloud activity.•At 1.6 μm a bright ring appeared at −66 degrees latitude.•The South Polar Wave (−60 deg) at 0.467 μm gained a bright band to the north.•The South Polar Wave’s speed is consistent with results from a decade before.
NaCl and KCl in Io’s Atmosphere Redwing, Erin; de Pater, Imke; Luszcz-Cook, Statia ...
The planetary science journal,
10/2022, Letnik:
3, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Abstract
We present the first comprehensive study of NaCl and KCl gases in Io’s atmosphere in order to investigate their characteristics and infer properties of Io’s volcanoes and subsurface magma ...chambers. In this work, we compile all past spectral line observations of NaCl and KCl in Io's atmosphere from the Atacama Large Millimeter/submillimeter Array and use atmospheric models to constrain the physical properties of the gases on several dates between 2012 and 2018. NaCl and KCl appear to be largely spatially confined, and for observations with high spectral resolution, the temperatures are high (∼500–1000 K), implying a volcanic origin. The ratio of NaCl:KCl was found to be ∼5–6 in 2015 June and ∼3.5–10 in 2016 June, which is consistent with predictions based on observations of Io's extended atmosphere and less than half the Na/K ratio in chondrites. Assuming these gases are volcanic in origin, these ratios imply a magma temperature of ∼1300 K, such that the magma will preferentially outgas KCl over NaCl.
We present 1 mm observations constructed from Atacama Large (sub)Millimeter Array (ALMA) data of SO2, SO, and KCl when Io went from sunlight into eclipse (2018 March 20) and vice versa (2018 ...September 2 and 11). There is clear evidence of volcanic plumes on March 20 and September 2. The plumes distort the line profiles, causing high-velocity ( 500 m s−1) wings and red-/blueshifted shoulders in the line profiles. During eclipse ingress, the SO2 flux density dropped exponentially, and the atmosphere re-formed in a linear fashion when reemerging in sunlight, with a "post-eclipse brightening" after ∼10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO2, the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO2 is the dominant source of SO. Disk-integrated SO2 in-sunlight flux densities are ∼2-3 times higher than in eclipse, indicative of a roughly 30%-50% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are N (1.5 0.3) × 1016 cm−2 and T 220-320 K both in sunlight and in eclipse, while the fractional coverage of the gas is two to three times lower in eclipse than in sunlight. The low-level SO2 emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of noncondensible gases preventing complete collapse of the SO2 atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO2, but simultaneous presence of KCl over Ulgen Patera.
NaCl & KCl in Io's Atmosphere Redwing, Erin; de Pater, Imke; Luszcz-Cook, Statia ...
arXiv.org,
09/2022
Paper, Journal Article
Odprti dostop
We present the first comprehensive study of NaCl and KCl gases in Io's atmosphere in order to investigate their characteristics, and to infer properties of Io's volcanoes and subsurface magma ...chambers. In this work, we compile all past spectral line observations of NaCl and KCl in Io's atmosphere from the Atacama Large Millimeter/submillimeter Array (ALMA) and use atmospheric models to constrain the physical properties of the gases on several dates between 2012 and 2018. NaCl and KCl appear to be largely spatially confined and for observations with high spectral resolution, the temperatures are high (~500-1000 K), implying a volcanic origin. The ratio of NaCl:KCl was found to be ~5-6 in June 2015 and ~3.5-10 in June 2016, which is consistent with predictions based on observations of Io's extended atmosphere, and less than half the Na:K ratio in chondrites. Assuming these gases are volcanic in origin, these ratios imply a magma temperature of ~1300 K, such that the magma will preferentially outgas KCl over NaCl.
Using near-infrared observations of Neptune from the Keck and Lick Observatories, and the Hubble Space Telescope in combination with amateur datasets, we calculated the drift rates of prominent ...infrared-bright cloud features on Neptune between 2018 and 2021. These features had lifespans of \(\sim 1\) day to \(\geq\)1 month and were located at mid-latitudes and near the south pole. Our observations permitted determination of drift rates via feature tracking. These drift rates were compared to three zonal wind profiles describing Neptune's atmosphere determined from features tracked in H band (1.6 \(\mu m\)), K' band (2.1 \(\mu m\)), and Voyager 2 data at visible wavelengths. Features near \(-70 \deg\) measured in the F845M filter (845nm) were particularly consistent with the K' wind profile. The southern mid-latitudes hosted multiple features whose lifespans were \(\geq\)1 month, providing evidence that these latitudes are a region of high stability in Neptune's atmosphere. We also used HST F467M (467nm) data to analyze a dark, circumpolar wave at \(- 60 \deg\) latitude observed on Neptune since the Voyager 2 era. Its drift rate in recent years (2019-2021) is \(4.866 \pm 0.009 \deg \)/day. This is consistent with previous measurements by Karkoschka (2011), which predict a \(4.858 \pm 0.022 \deg\)/day drift rate during these years. It also gained a complementary bright band just to the north.
We present 1-mm observations constructed from ALMA Atacama Large (sub)Millimeter Array data of SO\(_2\), SO and KCl when Io went from sunlight into eclipse (20 March 2018), and vice versa (2 and 11 ...September 2018). There is clear evidence of volcanic plumes on 20 March and 2 September. The plumes distort the line profiles, causing high-velocity (\(\gtrsim\)500 m/s) wings, and red/blue-shifted shoulders in the line profiles. During eclipse ingress, the SO\(_2\) flux density dropped exponentially, and the atmosphere reformed in a linear fashion when re-emerging in sunlight, with a "post-eclipse brightening" after \(\sim\)10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO\(_2\), the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO\(_2\) is the dominant source of SO. Disk-integrated SO\(_2\) in-sunlight flux densities are \(\sim\)2--3 times higher than in-eclipse, indicative of a roughly 30--50\% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are \(N \approx (1.5 \pm 0.3) \times 10^{16}\) cm\(^{-2}\) and \(T \approx 220-320\) K both in-sunlight and in-eclipse, while the fractional coverage of the gas is 2--3 times lower in-eclipse than in-sunlight. The low level SO\(_2\) emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of non-condensible gases preventing complete collapse of the SO\(_2\) atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO\(_2\), but simultaneous presence of KCl over Ulgen Patera.
Using archival near-infrared observations from the Keck and Lick Observatories and the Hubble Space Telescope, we document the evolution of Neptune's cloud activity from 1994 to 2022. We calculate ...the fraction of Neptune's disk that contained clouds, as well as the average brightness of both cloud features and cloud-free background over the planet's disk. We observe cloud activity and brightness maxima during 2002 and 2015, and minima during 2007 and 2020, the latter of which is particularly deep. Neptune's lack of cloud activity in 2020 is characterized by a near-total loss of clouds at mid-latitudes and continued activity at the South Pole. We find that the periodic variations in Neptune's disk-averaged brightness in the near-infrared H (1.6 \(\mu\)m), K (2.1 \(\mu\)m), FWCH4P15 (893 nm), F953N (955 nm), FWCH4P15 (965 nm), and F845M (845 nm) bands are dominated by discrete cloud activity, rather than changes in the background haze. The clear positive correlation we find between cloud activity and Solar Lyman-Alpha (121.56 nm) irradiance lends support to the theory that the periodicity in Neptune's cloud activity results from photochemical cloud/haze production triggered by Solar ultraviolet emissions.
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