Millions of miles away, in the far North of Mars, the greatest marketer of this young century is slowly dying in the cold and dark. A dust-storm is covering its photovoltaic panels, its power is draining and NASA has switched it into 'Lazarus' mode. The long Martian winter is setting in, we probably won't hear from it again. If you're one of the 40,000 people subscribed to the Mars Phoenix Lander's twitter stream you'll know exactly what I'm on about, the rest of you might need some explanation. Let's start with twitter - it's a simple service that lets you tell your friends (and other interested people) what you're up to in 140 characters or less. Via your phone or computer. It started off as a person to person thing, but fairly quickly all sorts of other stuff started to get squeezed down the twitter pipe; news headlines, the shipping forecast, news of whether Tower Bridge was opening or not. And, back in May, the Mars Lander was added to the list. It started as just another bit of the NASA effort to get the world interested in space again. A Jet Propulsion Lab staffer was asked to submit twitters on behalf of the Lander, but she did it so well, working in her own time, adopting an energetic first-person voice that she amassed an enthralled audience of 40,000 people - all for a media cost of zero. The Mars Phoenix Lander is a textbook example of how to use social media tools to delight an audience. Firstly, it was human and fun. The first person voice of the Lander meant it was accessible to all ages and education levels. You didn't need to be a rocket scientist. For example, the Lander announced the discovery of water like this: "Are you ready to celebrate? Well, get ready: We have ICE!!!!! Yes, ICE, *WATER ICE* on Mars! w00t!!! Best day ever!!". OK, so it's a bit juvenile, but it's exciting. It's how geeky scientists talk. And it was followed up with good, sensible, scientific explanation. Secondly, Mars Phoenix talked back. Questions asked on twitter were passed to the team running the Lander and answered swiftly and concisely, 140 characters is great discipline and people loved being involved in a conversation with another planet. Thirdly, the Lander team kept looking for opportunities to extend the story. As the Lander dies there's now an epitaph competition being run via twitter. The current favourite is "Veni, vidi, fodi. (I came, I saw, I dug)". Getting that many people interested in something, for no money, with no professional help, is what the social media revolution is all about. And the Mars Phoenix Lander is its first bona fide hero. The people of Earth salute you.