An illustration of Philae (right) detached from Rosetta (left) and falling towards the comet 67P/Churyumov–Gerasimenko (background). Illustration: ESA
Show Hide image

Rosetta, Philae and the comet: what you need to know about today's historic space mission

Some background while we wait for the ESA's probe to touch down on the comet's surface.

UPDATE (16:04 GMT): Philae has landed!

This morning at 09:03 (GMT) the Rosetta probe successfully detached its main payload - the Philae lander. About the size of a washing machine, Philae is now drifting down towards the surface of the comet 67P/Churyumov-Gerasimenko, which is currently out beyond the orbit of Mars, some 670 million km from the Sun.

It will take seven hours or so for Philae to become the first spacecraft to land on a comet. The European Space Agency is running informational programs all day on a livestream on its website - which you can watch here - and touchdown is expected to come at around 16:00 (GMT). It's going to be worth tuning in to the livestream beforehand to watch it happening in real-time.

Here's some background to today's big event:

The comet: The target of the mission today is a comet called 67P/Churyumov-Gerasimenko, named after the two Russian astronomers who discovered it in 1969. It's just over 4km across, takes 6.45 years to orbit the Sun, and one of the most wonderful discoveries of the mission so far is that it looks a little bit like a rubber duck. Here's what it would look like if it was hovering over central London:

Image: ESA

Rosetta: The European Space Agency's probe was first planned out in the mid-1990s, and launched in 2004. Today's event has been at least 20 years in the making, if not longer, and it is an extraordinary achievement of science and engineering. 67P/C-G is currently on the inward part of its orbit around the Sun, but like many comets it orbits in a highly elliptical fashion relative to Earth. The reason it's taken ten years to get Rosetta in position is that the probe had to make multiple passes around the Sun, Earth and even Mars to give it gravity boosts in the correct direction. Here's a video show what happened:

Now, Rosetta is orbiting the Sun along the same orbital path as the comet - but the final steps to get into that position were extremely tricky, with the engines required to make adjustments with a series of triangular orbits to ensure it got as close as possible. The comet's gravity is quite weak, so it was never going to be as easy as it is to, for example, put a satellite into orbit around the Moon:

Image: ESA

Of the data expected to be collected over the duration of the entire mission, most will come from Rosetta. It has extensively mapped the comet's surface and density from different heights, measured how it reacts to the solar wind, and analysed the dust and gasses it has flown through in its wake. The expectation is that Rosetta will remain in a tight orbit of 10km in height around the comet as it travels in towards and around the Sun, giving crucial insight into the development and structure of the tail that will form as it heats up and sheds mass. ESA scientists hope for at least another year and a half of study from Rosetta until either the damage from the flying debris gets too great or the solar panels are coated with too much dust to provide energy - but there is every possibility it could survive longer than that.

Comets are fragments of the early Solar System - examples of the kinds of lumps of rock and ice which collided together billions of years ago to form the planets as we know them, and as such analysing them can reveal hugely significant facts about what our place in the universe was like when the Sun was first born. There is even the possibility of settling the question of whether life-giving minerals and chemicals - including water - were "seeded" on Earth by comets in its early past, making them essential building blocks for life. It is very literally a mission of immense historic importance.

It's also worth noting the symbolism of this mission, being as it is arguably the European Space Agency's finest work so far (or, at least, fingers are crossed for the landing). Philae's landing will come a day after the hundredth anniversary of the European continent tearing itself apart in one of the bloodiest conflicts ever known; a hundred years later, the nations of Europe are working together for the betterment of scientific research, and to further understand our shared origins. We should celebrate this.

Philae: The lander doesn't have any engines or thrusters of its own, so mission controllers this morning had to time its release from Rosetta extremely carefully. We know that it worked successfully, and Philae is currently drifting like an extremely slow baseball pitch towards the comet's surface.

Since it doesn't have any way of propelling itself, the plan for when it reaches the surface is like something out of a movie. It's going to fire a harpoon gun at the surface to anchor itself, and then, when it manages to winch itself down, drills in each of its three legs will dig downwards as well, giving Philae a solid chance of not bouncing off back into space, helpless. (This is a real worry - the Japanese probe Hayabusa-1 had a lander called Minerva which was meant to land on an asteroid in 2005, but it missed and floated away.)

Signals from Earth also take roughly half an hour to reach both Rosetta and Philae, so it has to do this completely on auto-pilot. Part of the problem with Rosetta being such a success so far is that it has revealed the existing dichotomy between "asteroid" (a big rock) and "comet" (a big snowball) isn't quite right - the stunning pictures that Rosetta has taken so far show it to be quite a rocky and dusty place. Philae's harpoon was designed for ice, not rock, or dust. ISS astronaut Alexander Gerst filmed a video explaining the harpoon, which is nice:

What next?: You can watch the ESA livestream, which should be returning video and images from Philae as it happens. Randall Munroe of xkcd is also doing a "live cartoon" of sorts, if you want something a bit different. And, while waiting, some of the ESA mission scientists are shaving their heads in support for pancreatic cancer research - feel free to support them.

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

Show Hide image

Why the philosophy of people-rating app Peeple is fundamentally flawed

The app claims that “character is destiny”, and that we should be constantly judged based on our past interactions with others. But do we really believe that? 

Yesterday, you were probably one of the millions around the world who recoiled from their screen in blank-eyed horror at the news: Peeple, an app to be launched in November, will let others rate you, publicly, on the internet, and there's nothing you can do about it. You can't opt out, and you don't need to join in order to be rated on a scale of one to five by colleagues, friends, and romantic partners. That boy whose girlfriend you stole? He can review you. The boss you swore at as you quit? Her, too. Those people in your life who think you're just a bit average? Expect a lukewarm three stars from them.

Of all the online rage at the app's announcement, perhaps the most was directed at the fact that you can't remove your own profile. Other users need only submit your mobile number and name to create your page, and you have no control about who posts on there. Reviews of two stars or less are invisible to the public for 48 hours, and you have the chance to review them and try to "work it out" with the rater. Once that time is up, though, the negative reviews appear for all to see. You can comment on them to defend your corner, but unless they break the app's rules, you can't delete them.

There are all kinds of problems with Peeple's premise. Despite its founders' promises that bullying and harassment won't be tolerated (helped slightly by the fact that users must be over 21 and use their full name and Facebook profile to comment), it seems impossible that they'll be able to moderate this effectively. And as we've learned from sites like TripAdvisor or Yelp, the majority of reviews are from those seeking to boost the company's reputation, rivals, or angry customers - it's rare to see one that's balanced and helpful.

Yet the biggest flaw of all is the assumption that public rating and shaming has a place, or is even acceptable, in our society. There's something fundamentally broken in the app's presmise, which is summarised in its tagline, "character is destiny".  As western society has moved on from earlier ages where people were fundamentally changed in the eyes of the law and public into "criminals" by virtue of their deeds, or a time where a woman was utterly defined by her sexual acts, we've ceased to accept this as truth. The app's whole set-up assumes that someone who has offended a co-worker is likely to do it again, or a positive review from a partner makes it likely you'll enjoy a good relationship with them. As a society, we accept that some violent criminals are likely to re-offend, but we also see the value of rehabilitation, and can accept that people make mistakes they're unlikely to repeat. 

The dark side of social media is that it moves us backwards on this front. It allows permanent imprints of our online lives to be seen by everyone, to the extent where they seem to represent us. Victims of cyberbullying terrified that naked photos of them will be released, or people who make public gaffes on social media, become reduced to and defined by single acts. The mental health deterioration (and sometimes  suicide) that follows these shamings hints at how unnatural it is for single actions to change lives in such disproportionate ways. 

Jon Ronson, author of So you've been publicly shamed, which cleverly links the current culture of internet shaming with a legal past where criminals were shamed indefinitely as criminals for a single illegal act, seems chilled by the prospect of Peeple:

As one review of Ronson's book noted:

As Ronson makes patently clear, all these people’s punishments by far outweighed the gravity of their so-called crimes. In fact, having researched the history of public shaming in America in the Massachusetts Archives, he can only conclude that Lehrer, for one, was humiliated to a degree that would have been thought excessive even in the 18th century, the Puritans of New England having seemingly worked out that to ruin a person in front of his fellows is also to refuse him a second chance in life.

As Ronson explores in his book, extreme public shaming doesn't make us better people, or encourage us not to repeat offend: it shuts us down and exiles us from society in a way that benefits no one. (This makes Peeple's URL – – seem grimly ironic). What Ronson calls "chronic shame" occurs when our regretted actions harden into something far greater, something we allow to become part of ourselves. As Gershen Kaufman, a scholar of shame, notes:  "Shame is the most disturbing experience individuals ever have about themselves; no other emotion feels more deeply disturbing because in the moment of shame the self feels wounded from within."

We also shouldn't be forever defined by a clutch of "good" actions, or people who see some benefit in leaving us gushing reviews. Those who measure their worth through social media come to rely on the endorphins sparked by small online interactions and boosts to their confidence, at the expense of the more slow-burning satisfaction of real life. A single person's thoughts about us are relatively inconsequential, whether positive or negative - but they're given far greater weight on the internet  by virtue of their permanence and publicity.

In Mary Gordon's novella The Rest of Life, a character wishes that someone had told her earlier that "the world is large and will absorb the errors you innocently make". If we're to avoid tearing each other to pieces, we need to make sure that this remains the case. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.