Astronomy

10 ASTRONOMY • SEPTEMBER 2017

T

he seven new Earth-

sized planets around

TRAPPIST-1, a red

dwarf star 39 light-

years away, recently

renewed public speculation

about extraterrestrials. Sixty

years ago, the consensus among

astronomers was that life’s

earthly genesis was so convo-

luted and unlikely that we may

be alone in the universe. For

some physicists like Enrico

Fermi, negative results from

the Search for Extraterrestrial

Intelligence (SETI) reinforced

that pessimism. But these days,

very few astronomers feel that

way. The current groupthink

is that the universe probably

teems with life.

Early discovery steps in the

near future will include spectro-

scopic space telescopes studying

exoplanet atmospheres, offering

the ability to study their compo-

sition. Earth’s habitable atmo-

sphere exists solely because of

photosynthetic plants exchang-

ing carbon dioxide for oxygen.

It would therefore be very

encouraging if we detected oxy-

gen around another world, as it

may point the way toward life.

But what is life? Scientists

can’t agree on a definition. Are

viruses alive? They have no

metabolism, they don’t feed

themselves, and many biologists

regard them as inanimate. Yet

their RNA coding forces host

cells to make lots of viral copies.

And does life begin through

chemistry? If certain occur-

rences cause life to arise from

non-living components, we

want to know if it happens

readily. In other words, is life

easy? Or does it require

extremely unlikely events?

STRANGEUNIVERSE

The coming decades may bring proof of aliens.

But will we know what we’re looking at?

BY BOB BERMAN

Finding aliens

A good argument for life

being “easy” is that earthly life

began almost as soon as it was

possible. After the molten Earth

cooled, there came a long

period when asteroids and com-

ets pummeled our surface. This

violence stopped some 4 billion

years ago. And bingo, the earli-

est fossils date from right then,

within 200 million years of

when it was first possible.

That’s awfully quick.

A good counterargument,

which makes the case for life

being “hard,” is that life-origi-

nation or abiogenesis happened

only once (that we know of ).

Every earthly creature is a

descendant of that first ances-

tral organism. We know this

because all life, from elephants

to bacteria, share remarkable

genetic similarities. They’re all

made of amino acids and sugars

with the same kinds of spirals

or asymmetries. Amino acids

can come with left- or right-

handed twists, called chirality.

But on Earth, life only uses

amino acid molecules with left-

handed twists, and is limited to

a right-handed direction in all

its sugars and DNA — the same

as a corkscrew.

If life started a second time

from scratch, it likely would

show differences in such chiral-

ity. Now, there are at least

6 million species of bacteria

(even if only 100,000 have had

their genomes sequenced). But

every single microbe, plant and

animal we’ve examined is a

descendant of that first life cre-

ation. The point: Why didn’t

life start a second time, a third,

or a hundredth? Four billion

years have passed, and yet life

originated only once. This sug-

gests that abiogenesis is not

easy, but hard.

So which is it? Fred Hoyle,

who coined the term “Big

Bang,” described an accidental

birth of life as akin to a tornado

sweeping through a junkyard

and creating a jumbo jet.

Supporting this, Francis Crick,

the co-discoverer of DNA’s dou-

ble helix, described the origin

of life as “almost a miracle, so

many are the conditions which

would have had to have been

satisfied to get it going.” (He

wasn’t suggesting a spiritual

origin, merely that the process

is utterly baffling.) If abiogen-

esis is really so unlikely, then

even given the immense size of

the cosmos, it’s possible we’re

the only example.

Of course, this assumes abio-

genesis only happens acciden-

tally. But what if advanced

aliens are creating life, or if

nature has immense innate

intelligence? I just saw an amaz-

ing nature documentary called

Flying Monsters 3D by David

Attenborough, showing the first

f lying creatures from millions

of years ago. The earliest bird

wings had the same shape as

modern aircraft. That airfoil

configuration is necessary for

all f light, and requires a wing’s

upper surface to be convex. It’s

hard to see how evolution could

have created it. Unlike giraffes’

necks, where incremental

increases offered survival

advantages, a step-by-step pro-

cess wouldn’t work for a wing

design. A slightly wrong shape

would be useless and confer no

benefit. Some 400,000 cells

would all have to simultane-

ously mutate in just the right

way to create a properly shaped

wing. This defies an evolution-

ary hypothesis.

Occam’s razor might suggest

some baked-in, overarching

intelligence. I’m not invoking

spirituality, merely that the

effect of random collisions and

mutations is not always a work-

able answer. So perhaps nature

is inherently smart. We cannot

visually see this intelligence,

just as we cannot see electrical

fields; and yes, this is a minor-

ity viewpoint. But if true, then

the sky’s the limit for ETs.

It’s guesswork. We know of

life on only a single world, so

our sample size is one. And

when you try to draw a line on

a graph but you have just one

data point, well, good luck.

We’ll have no shortcuts when

we probe the planetary system

of TRAPPIST-1.

BROWSE THE “STRANGE UNIVERSE” ARCHIVE AT http://www.Astronomy.com/Berman.

Contact me about

my strange universe by visiting

http://skymanbob.com.

While SETI has been around since 1960, it has yet to turn up any conclusive proof

of intelligent life. The Wow! signal, pictured above, is one of the more mysterious

signals received, but it has never repeated or been conclusively identified. BIG EAR

RADIO OBSERVATORY AND NORTH AMERICAN ASTROPHYSICAL OBSERVATORY (NAAPO)

BUT WHAT IS LIFE? SCIENTISTS

CAN’T AGREE ON A DEFINITION.