Various anomaly detection methods utilizing different types of images have recently been proposed. However, anomaly detection in the field of planetary science is still done predominantly by the human eye because explainability is crucial in the physical sciences and most of today's anomaly detection methods based on deep learning cannot offer enough. Moreover, preparing a large number of images required for fully utilizing anomaly detection is not always feasible. In this work, we propose a new framework that automatically detects large bow-shaped structures~(stationary waves) appearing on the surface of the Venus clouds by applying a variational auto-encoder~(VAE) and attention maps to anomaly detection. We also discuss the advantages of using image augmentation. Experiments show that our approach can achieve higher accuracy than the state-of-the-art methods even when the anomaly images are scarce. On the basis of this finding, we discuss anomaly detection frameworks particularly suited to physical science domains.