  We report, for the first time, the impact of an interplanetary coronal mass
ejection (ICME) on the recently discovered O($^1$S) 557.7 nm dayglow emission
in the Martian atmosphere. Although there are only a few studies on the
seasonal variation are available in the literature, the impact of ICME on 557.7
nm dayglow emission has not been investigated so far. Using the instruments
aboard ExoMars-TGO and MAVEN spacecrafts, we show that the primary emission
peak (75-80 km) remains unaffected during the ICME event compared to
quiet-times. However, a noticeable enhancement has been observed in the
brightness of secondary emission peak (110-120 km) and the upper altitude
region (140-180 km). The enhancement is attributed to the increased solar
electrons and X-ray fluxes, augmenting the electron-impact process and causing
the enhancement in the brightness. These analyses have an implication to
comprehend the role of intense solar transients like ICME on the Martian
dayglow emissions.
