Comets are extremely old. Older than humanity. Older than the Earth.
They are leftover remnants of the huge primordial cloud of gas, dust and ice that gave birth to the sun and all the planets of our solar system.
Located on the outer fringes of that cloud, they were too far away to be melted by radiation from the sun and too sparsely spread to coalesce into a planet. They have remained unchanged, frozen remnants of our birthplace for more than 4 billion years.
Studying comets is studying our own origins. It’s like walking into a bakery after everyone is gone and all the pies are in the oven. By looking at the mess on the floor, you can see all the ingredients that went into the pies - the flour, scraps of fruit, sugar, etc. - and from that figure out what kind of pies are being made.
Determining all the original ingredients is also something you can’t necessarily do by looking at the end result. In the same way that baking changes the form of the pies, planets have evolved and changed since they were born, due to effects from the sun, volcanic activity, changing atmospheres and oceans.
The comets carry those original ingredients that made us who we are. Observations from the ground and other spacecraft that have flown close to comets show that they contain a lot of water ice as well as carbon-based molecules such as amino acids which, when put together, can form part of the structure of DNA.
That is not to say there is life in comets, but some scientists suggest that the ingredients for life on Earth could have been delivered by these celestial bodies, along with much of the water for that life to thrive in.
That’s why there is so much excitement now over the ability of the Philae lander to dig directly into the surface of the comet and analyze what it’s really made of.
This is primary exploration, where humans, through the artificial senses of robots, are literally going where no one has gone before.
It is fundamental science, where we discover basic facts about who we are and where we came from.
It may not affect your life directly today, but knowledge for the sake of knowing it is always valuable, and when exploring the unknown, who knows what will come out of it.
Front row seat
Another bonus of this mission is that the comet will change as it swings past the sun.
The water ice will vaporize, producing ice geysers that will erupt from the surface and blow out into space, producing the beautiful tails we see gracing our skies. Both the Philae lander and orbiting Rosetta spacecraft will be able to watch these events in real time.
As the comet loses mass from the inside, will the ground collapse like a sinkhole, will hoodoos form, or will the comet actually break apart?
Comet 67P has a dumbbell shape with a narrow neck connecting two lobes. That neck could erode to the point where it becomes too weak to hold the rotating body together. Imagine watching a small world coming apart from right there on the ground.
For now, everyone involved with the mission is happy just to be on 67/P. Like vacationers arriving at a new destination, what happens next will be full of surprises. We are fortunate to be along for the ride.