You wanted to discuss your latest results?”

Yes; I don’t know what to make of them.”

What’s the issue?”

I found unusual patterns of low energy radiation, well below ionising frequencies, coming from the solar system I’ve been examining.”

You’ve ruled out it coming from the star, I suppose?”

Yes – that emits fairly normal levels of radiation of all frequencies so far as I can tell, no particular patterns beyond flares, bursts, that sort of thing. These are very specific, very complex patterns, unlike anything of a known natural origin.”

That could be just the sign life we’ve been looking for. Weren’t there some promising looking large gaseous planets in the solar system that you were looking at?”

Yes, that’s the trouble. It’s not coming from one of the gaseous planets. It’s coming from a small, rocky planet much nearer the star.”

A rocky planet? Are you sure?”

Yes. I thought that it was one of the gaseous planets, too, until I observed that all the signals were blocked when one of those very gaseous planets passed in front of its orbit, for them only to come back again the moment that it passed.”

It’s possible, I suppose, that life might form on a rocky planet in the right conditions, although it’d be very difficult.”

I wondered about that. But this planet is far too close to the star. The temperatures would be too high, even at the poles: well above the boiling point of nitrogen.”

Could it be tidally locked? If the side of the planet that always faces away from the sun had large pools of liquid nitrogen on its surface, then –”

It can’t be tidally locked; the orbit’s all wrong, I checked that, too. Every part of that planet will be exposed to the heat from that star so often that there won’t be any liquid nitrogen anywhere.”

It’s hard to see how life could have evolved without liquid nitrogen.”

And there’s more. Although it’s not a gaseous planet, it seems to be surrounded by a huge cloud of gas. That’d make the planet even hotter – even mercury would melt on its surface.”

That is hot.”

Yes – and the composition of the gas: the spectrum analysis shows that it’s mostly nitrogen, but there’s another gas in there as well: oxygen.”

Oxygen? That’s highly reactive. That’d tear apart the delicate molecules on which life is based given half a chance. How much of it is there?”

About a fifth of the gas cloud seems to be oxygen.”

A fifth? That’d destroy any known living organism in seconds. But perhaps there are some extremophiles living near the poles that have evolved to block out all the oxygen and tolerate the extreme heat?”

Possibly. But there’s another problem. Judging by the density calculations, the planet seems to be made mainly of iron.”

Iron? That’s harmless enough.”

Of itself, yes. But the planet’s orbit is perturbed. It doesn’t match what I’d expect if the planet were solid.”

What’s the significance of that”?

One thing that we know about these rocky planets is that the younger ones can have liquid interiors. They cool over time and solidify, but this one seems to have an interior that’s still at least partly liquid.”

Why is that a problem?”

Liquid iron on that scale would generate huge magnetic fields, like nothing we’ve seen in our own solar system. Magnetic fields that strong would block almost all of the cosmic radiation.”

Oh, I see, yes, that is a problem. How would the life forms get the energy that they need to live if all the cosmic radiation were blocked by this giant magnetic field?”


There’s not a single known example of a silicon based life form drawing energy from a source other than cosmic rays.”

And that’s the difficulty.”

Yes, I see that it’s a very taxing problem.”

I was wondering, though. Perhaps we’ve been looking at this all the wrong way.”

What do you mean?”

We’ve been looking the whole time for life forms just like ourselves – silicon and mercury based. We look for planets that are in just the right position, far enough away from the star to have liquid nitrogen, mainly gaseous, or at least vapourous in composition, and with access to plentiful cosmic radiation. A sort of Goldilocks zone, if you like.”

Yes, indeed; just the right conditions for life to form.”

But could it not be said that life on this planet evolved with the sort of chemistry that it did precisely because that suited the conditions in which it first came into being? There’s no reason in principle that life has to be based on silicon and mercury, is there? It could be based on anything that allows for self replication. All that it really needs, surely, is an environment that is stable enough to allow complex, self-replicating molecules to exist for long enough to evolve, but not so stable that they won’t be created in the first place? The heat of the star could provide the energy if all the cosmic rays were blocked.”

Those are very grand ideas, but what other form of chemistry could support self-replication? I know that some experiments recently have suggested that possibly arsenic could replace mercury in certain conditions, but even those organisms couldn’t survive the sort of temperatures you’re talking about on that planet. So far as we know, no living organism could withstand heat anywhere near enough to satisfy its energy requirements. That’s the beauty of ionising radiation.”

I suppose that you must be right. It was a far-fetched idea. But what of these low-energy radiation signals?”

That is the conundrum. But, wait; didn’t you say that the planet had a liquid iron core?”


Could that possibly account for these signals? We haven’t seen any iron planets in our solar system; for all we know, all that iron sloshing about could generate all kinds of interference patterns.”

Yes – or more likely, perhaps, the magnetic field is somehow filtering and distorting the star’s radiation, although I’m not quite sure how that’d work. Nobody’s done any modelling on that. But that does sound more plausible than complex life forms on a hot, rocky planet, you’re right. It’s a pity, though. I did wonder whether this might have been it.”

The more that I work on this project, the more that it seems that we really are alone in the universe after all.”