in General Knowledge 4 billion years ago, Mars had an ocean covering… by Web Desk August 30, 2016, 9:48 am 47 Views 4 billion years ago, Mars had an ocean covering 19% of the planet’s surface. Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website By using this form you agree with the storage and handling of your data by this website. *