Five years ago, a spacecraft named Osiris-REx came face-to-face with an asteroidA small body in space, made of metal and rock material. Asteroids usually orbit the sun, but if knocked off course they can be drawn into Earth's gravity and fall towards it. half a kilometre across. For two years, it patiently scanned the surface, looking for the right site, before finally releasing a little capsule that drifted towards the vast rock and collected a tiny sample of just 250 grams.

On Sunday, that capsule finally arrived home, touching down gently in the UtahA mountainous state in the west of the USA. More than half its inhabitants are Mormons, who founded its capital, Salt Lake City. desert. Now scientists hope its hamster-sized sample will help them unlock the mysteries of life, the universe and everything.

The asteroid, named Bennu, is made up largely of carbon compoundsChemical substances that contain carbon. . This is important because another thing that is made up largely of carbon compounds is us.

Scientists believe this is no coincidence. The building blocks of life might have been deposited here billions of years ago through impacts by asteroids like Bennu.

Bennu has not changed much since the solar system was formed more than 4.5 billion years ago. That means studying it is like going back in time to the formation of the Earth. It could give us invaluable information about how we came to be.

If Bennu offers us the key to life on Earth, it might tell us something about death. There is a one in 2,700 chance that Bennu might one day collide with our planet.¹

That might not seem like much, but the stakes are very high. If Bennu hit the Earth it would release 24 times as much energy as the biggest nuclear bomb we have ever built.

If it hit the ocean, it would create a megatsunamiA huge and destructive ocean wave, tens or hundreds of metres high, caused by a great displacement of water. that would devastate much of the coast. The shockwaves would knock down whole cities. It could even split continents in two.²

So even if the chances of an impact are slim, it is worth knowing how to stop one. NasaThe National Aeronautics and Space Administration, responsible for the US space programme. hopes studying the sample will give us the tools we need to do this.

No wonder the team behind Osiris-REx is over the moon. But some philosophers are less convinced.

They are worried that these days, when people talk about finding the "key" to life, they almost always mean finding out how life came to be.

The problem, they argue, is that science is not really capable of answering the question. It might one day be able to tell us how life came to be, but it cannot explain why we live.

They think the fact we want space to tell us why we exist shows that we are no longer confident we can find a reason for our existence here on Earth. It speaks to our deep pessimism about the human race and our future on the planet.

To understand why we live, we need to engage with difficult philosophical questions about what our lives should be all about. Relying on science to tell us why we live risks tipping us into nihilismThe belief that life is meaningless. . If our only answer to this question is that an asteroid happened to collide with Earth, that gives us no guidance about the right kind of life to pursue.

Thousands of years ago, when humans could not explain why they were here, they looked to the heavens for an answer. It is telling, they say, that modern-day scientists are doing the same.

Yes: Scientists have long believed the building blocks of life might have started in space. This is our best chance yet to prove it and begin to understand where life came from.

No: Science cannot hold the key to life. The question of why we live is a philosophical one, and answering it will mean engaging with difficult questions about who we are and how we should behave. This is just a cop-out.

Or... Science and philosophy are looking to do different things here. It is interesting and useful to know where life came from. But that should not be a substitute for thinking about why we live.