meanwhile, other astronomers were looking for signs of life on other planets. in 1822, franz von gruithuisen thought he saw a giant city and evidence of agriculture on the moon, but astronomers using more powerful instruments refuted his claims. gruithuisen also believed he saw evidence of life on venus. ashen light had been observed on venus, and he postulated that it was caused by a great fire festival put on by the inhabitants to celebrate their new emperor. later he revised his position, stating that the venusians could be burning their rainforest to make more farmland.