10. Helium. Its spectroscopic lines were first noted by French astronomer Jules Janssen during a total solar eclipse on August 18, 1868. Several weeks later British astronomer Norman Lockyer noticed the same lines while observing the Sun without a total solar eclipse. The existence of helium on Earth was finally confirmed in 1895.
Taken near the entrance of Hawai`i Volcanoes National Park (which is now closed) on May 15, 2018, at 11:28 am.