Small, cool planets represent the typical end-products of planetary formation. Studying the architectures of these systems, measuring planet masses and radii, and observing these planets' atmospheres during transit directly informs theories of planet assembly, migration, and evolution. Here we report the discovery of three small planets orbiting a bright (K s = 8.6 mag) M0 dwarf using data collected as part of K2, the new ecliptic survey using the re-purposed Kepler spacecraft. Stellar spectroscopy and K2 photometry indicate that the system hosts three transiting planets with radii 1.5 -2.1 R ⊕ , straddling the transition region between rocky and increasingly volatile-dominated compositions. With orbital periods of 10-45 days the planets receive just 1.5-10× the flux incident on Earth, making these some of the coolest small planets known orbiting a nearby star; planet d is located near the inner edge of the system's habitable zone. The bright, low-mass star makes this system an excellent laboratory to determine the planets' masses via Doppler spectroscopy and to constrain their atmospheric compositions via transit spectroscopy. This discovery demonstrates the ability of K2 and future space-based transit searches to find many fascinating objects of interest.

The detection of phosphine (PH3) in the atmosphere of Venus has been recently reported employing mm-wave radio observations 1 , hereafter G2020. In this report, we identify several fundamental issues in the analysis and interpretation of the spectroscopic data, which would mean that the detection PH3 is not supported by our analysis of the data.The measurements target the fundamental first rotational transition of PH3 (J=1-0) at 266.944513 GHz, which was observed with the James Maxwell Clark Telescope (JCMT) in June 2017 and with the Atacama Large Millimeter/submillimeter Array (ALMA) in March 2019. This line is very close to the SO2 (J=309,21-318,24) transition at 266.943329 GHz (only 1.3 km/s away from the PH3 line) and therefore this SO2 line represents a serious source of contamination. The presented JCMT and ALMA datasets as presented in G2020 are at spectral resolutions comparable to the velocity separation of the two lines, and the line cores are several km/s in width, which does not permit spectroscopic separation of these two species.To explore the hypothesis that the observed 267 GHz feature is SO2, and not PH3, we employed the same VIRA45 temperature/pressure (T/P) profile used by G2020 ("extended Data Figure 8") and the G2020 SO2 profile ("extended Data Figure 9"). See further information about plausible Venus SO2 abundances and known variability in S1. As shown in Figure 1, we can fully explain the claimed "PH3" feature with their SO2 profile. For these simulations, we employed three independent radiative transfer analyses: the Planetary Spectrum Generator (PSG, https://psg.gsfc.nasa.gov) 2 , the Non-linear optimal Estimator for MultivariatE spectral analySIS (NEMESIS) 3 and the CfA planetary modeling tool 4 . The PSG radiative transfer analysis included the latest HITRAN SO2 line parameters for a CO2 atmosphere 5 , a layer-by-layer line-by-line study, and a full disk sampling scheme with 10 concentric rings. The NEMESIS analysis was also performed in line-by-line mode, and used the same line data with a 5-point Gauss-Lobatto disc-integration scheme. As described in G2020, there is some uncertainty in the line-shape parameters for the PH3 line in a CO2 atmosphere. HITRAN reports an air linewidth of 0.067 cm -1 /atm for this line, which could correspond to 0.12 cm -1 /atm for CO2 if we scale by the typical 1.8 scaling ratio observed for the SO2 lines 6 . G2020 employed the line shape for the NH3(J=1-0) line at 572.498160 GHz, which has a much greater linewidth of 0.2862 cm -1 /atm. This uncertainty in the linewidth has a dramatic impact on the inferred PH3 abundance, and our upper limit for the abundance of PH3 from these data (after removing SO2) ranges from < 5 ppb (3s) for 0.12 cm -1 /atm to < 12 ppb (3s) for 0.2862 cm -1 /atm (Figure 1). This upper-limit is consistent with the recent reports of non-detection of PH3 (< 5 ppb) at infrared wavelengths with TEXES/NASA-IRTF 7 .

An outburst of cloud activity on Neptune in 2015 led to speculation about whether the clouds were convective in nature, a wave phenomenon, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). The Hubble Space Telescope (HST) finally answered this question by discovering a new dark vortex at 45 degrees south planetographic latitude, named SDS-2015 for “southern dark spot discovered in 2015.” SDS-2015 is only the fifth dark vortex ever seen on Neptune. In this paper, we report on imaging of SDS-2015 using HST’s Wide Field Camera 3 across four epochs: 2015 September, 2016 May, 2016 October, and 2017 October. We find that the size of SDS-2015 did not exceed 20 degrees of longitude, more than a factor of two smaller than the Voyager dark spots, but only slightly smaller than previous northern-hemisphere dark spots. A slow (1.7–2.5 deg/year) poleward drift was observed for the vortex. Properties of SDS-2015 and its surroundings suggest that the meridional wind shear may be twice as strong at the deep level of the vortex as it is at the level of cloud-tracked winds. Over the 2015–2017 period, the dark spot’s contrast weakened from about to about , while companion clouds shifted from offset to centered, a similar evolution to some historical dark spots. The properties and evolution of SDS-2015 highlight the diversity of Neptune’s dark spots and the need for faster cadence dark spot observations in the future.

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The Large Binocular Telescope Interferometer mid-infrared camera, LMIRcam, imaged Io on the night of 2013 December 24 UT and detected strong M-band (4.8 μm) thermal emission arising from Loki Patera. The 22.8 m baseline of the Large Binocular Telescope provides an angular resolution of ∼32 mas (∼100 km at Io) resolving the Loki Patera emission into two distinct maxima originating from different regions within Loki's horseshoe lava lake. This observation is consistent with the presence of a high-temperature source observed in previous studies combined with an independent peak arising from cooling crust from recent resurfacing. The deconvolved images also reveal 15 other emission sites on the visible hemisphere of Io including two previously unidentified hot spots.