Happy Birthday to Mars Rover Curiosity, whose mission turned one year old today. It's been a big year for the little robot. Not only did Curiosity find the key ingredients necessary for life to be present on Mars, it also turned up evidence of an ancient streambed, many different types of rocks and soil, and even dangerously high levels of radiation.

But Curiosity is not the only one having an action-packed year. Here's what five similarly-aged start-ups have done in their first year on Earth. 

Medium and Branch (August 2012)

Last August, Twitter co-founders Evan Williams and Biz Stone announced the launch of two new start-ups: Medium and Branch

Medium is a publishing platform for sharing online content. However, unlike Twitter's timely 140-character bursts, Medium features longform content that rises to the top based on demand. Medium users can vote for their favorite pieces, and recently, Medium added a tool that allowed authors to solicit feedback prior to publishing their work. 

Branch, on the other hand, is designed as an online conversation platform--think virtual dinner table--that allows Twitter users to start a conversation on a given topic and invite specific other users to join. All participants can sign up to receive updates about the progress of the conversation. Branch went from private beta to public beta last August, and then in January of this year, it announced its Activity Feed, and kissed beta goodbye for good. 

Ouya (July 2012)

Ouya burst into existence with a bang--after setting a Kickstarter record for more than $3 million in funding in just 24 hours, it ending up raising $8.5 million overall for converting its model prototype into a production-ready video game console. Since then, it's been a rollercoaster year: Before its Kickstarter campaign even ended, Ouya announced that it was partnering up with OnLive to offer cloud-based games. In May, the company raised a $15 million venture round, led by Kleiner Perkins. In June, its long-awaited $99 Android-based console finally hit shelves. And this past weekend, the company was forced to apologize to backers who hadn't received the console before it landed in stores. 

Sidecar (June 2012)

Since launching in San Francisco last June, Sidecar has expanded its ride-sharing operations to include Seattle, Los Angeles, Chicago, Boston and Washington, DC. Sidecar, which differs from its competitors in that its fares are technically donations and its drivers aren't professionals, raised $10 million in Series A financing from Google Ventures and Lightspeed Venture Partners last October.

RebelMouse (June 2012)

RebelMouse, founded by Paul Berry, a former technology chief at Huffington Post, aims to fix the eternal headache of keeping up with numerous social media accounts. Instead, it aggregates all activity in one spot and in real time. Just weeks after its one-year anniversary, RebelMouse announced that it had raised $10.25 million in Series A funding. The start-up also topped 7 million uniques and, to date, more than 300,000 sites have been created.