TY - JOUR
T1 - Stringent upper limits of minor species at the cloud top of Venus: PH3, HCN, and NH3
AU - Encrenaz, T.
AU - Greathouse, T. K.
AU - Giles, R.
AU - Widemann, T.
AU - Bézard, B.
AU - Lefèvre, F.
AU - Lefèvre, M.
AU - Shao, W.
AU - Sagawa, H.
AU - Marcq, E.
AU - Arredondo, A.
PY - 2024
Y1 - 2024
N2 - Aims. Following several reports announcing the detection or
non-detection of minor species above the clouds of Venus, we have
searched for other possible signatures of PH3, HCN, and NH3 in the infrared range.
Methods. Since 2012, we have performed ground-based
observations of Venus in the thermal infrared at various wavelengths to
monitor the behavior of SO2 and H2O at the cloud top. We have identified spectral intervals where transitions of PH3 (around 955 cm−1), HCN (around 747 cm−1), and NH3 (around 951cm−1) are present.
Results. From the absence of any feature at these frequencies, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 3 ppbv for the PH3 mixing ratio, 0.5 ppbv for HCN, and 0.3 ppbv for NH3,
assuming that these species have a constant mixing ratio throughout the
atmosphere. Maps of the Venus disk recorded at the center position of
the lines show that there is no evidence for local detection anywhere
over the Venus disk.
Conclusions. Our results bring new constraints on the maximum
abundance of these species at the cloud top and in the lower mesosphere
of Venus.
AB - Aims. Following several reports announcing the detection or
non-detection of minor species above the clouds of Venus, we have
searched for other possible signatures of PH3, HCN, and NH3 in the infrared range.
Methods. Since 2012, we have performed ground-based
observations of Venus in the thermal infrared at various wavelengths to
monitor the behavior of SO2 and H2O at the cloud top. We have identified spectral intervals where transitions of PH3 (around 955 cm−1), HCN (around 747 cm−1), and NH3 (around 951cm−1) are present.
Results. From the absence of any feature at these frequencies, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 3 ppbv for the PH3 mixing ratio, 0.5 ppbv for HCN, and 0.3 ppbv for NH3,
assuming that these species have a constant mixing ratio throughout the
atmosphere. Maps of the Venus disk recorded at the center position of
the lines show that there is no evidence for local detection anywhere
over the Venus disk.
Conclusions. Our results bring new constraints on the maximum
abundance of these species at the cloud top and in the lower mesosphere
of Venus.
KW - Planets
KW - Planets and satellites: atmospheres
KW - Planets and satellites: composition
KW - Satellites: terrestrial planets
U2 - 10.1051/0004-6361/202451495
DO - 10.1051/0004-6361/202451495
M3 - Journal article
SN - 0004-6361
VL - 690
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A304
ER -