With the dearth of good real estate on Earth,
I’ve been considering alternatives. One obvious
candidate is Mars. However, in its current
orbit, it’s too nippy and the air is too
thin to satisfy anyone except Sherpas. How
much energy would it take to move Mars
into Earth’s orbit? Would it work better if we
moved Venus instead because of its similar
size to Earth? Please answer quickly as I need
to finalize my retirement plans.
—James Borowiec
I have to tell you, I admire the balls
behind this concept. We’ve already got
one planet pretty much hosed. Why not
go for two?
I assigned my assistant Una to look into
what it would take to haul Venus or Mars
into the same orbit as Earth. Una’s engineering
résumé is sparse in the planetary
relocation department, but I figured it
was just a matter
of moving some
decimal points.
To be on the
safe side, however,
she teamed
up with Noam
Izenberg, a planetary
scientist at the
Johns Hopkins
University
Applied
Physics
Laboratory.
Results:
Assuming
1. Mars
doesn’t rip
apart from the
stress of moving,
and 2. its moons,
Phobos and Deimos, come along
for the ride, we’re looking at close to 9.8 x
1031 joules of energy to drag it down by us.
That’s roughly the same kick as 234 trillion
100-megaton nuclear warheads. Moving
Venus would take still more energy—multiply
the above by 8.5.
Discouraged? Don’t give up so fast. One
idea out there is to change the orbit of a
good-sized asteroid or comet—about 100
kilometers in diameter—so that it swings
by one of the inner planets and then back
out to, say, Jupiter. As the cosmic tow
truck passes our target planet, it uses its
gravitational attraction to tug the planet in
the desired direction, then hurtles back to
slingshot around Jupiter, picking up more
energy in the process. Repeat a few thousand
times with a few score asteroids and
there you go: Mars in your backyard.
This technique has been proposed
as a way to drag Earth away from the
ever-brightening sun that otherwise will
eventually snuff out life on our planet. It
has some downsides, though. One is that,
each time the asteroid comes by, it’ll exert
a tidal force 10 times greater than the
moon’s, wreaking havoc on the oceans and
weather. Another is that some Poindexter
on the relocation team is bound to make a
unit conversion error along the way, and
when the asteroid slams into the Earth—well, that’ll be a real pisser. Luckily, we
don’t need to worry about things like
that if we’re moving Mars or Venus: If we
make one planet go boom, we’ve still got
a spare.
Once we get the planet where we want
it, though, we’ve still got our hands full.
However bad the environment on Earth is,
Venus’ is worse. Atmospheric pressure is
roughly 92 times ours, the planet has no
free oxygen or water to speak of, and the
surface temp is hot enough to melt lead.
Mars has an extremely thin atmosphere
but its temperature, while chilly, isn’t so
bad, and it’ll get warmer when it’s closer
to the sun. That alone might cause enough
melting at the Martian poles to release
ice-bound CO2 and create a greenhouse
effect. If not, we can always try focusing
the sun’s rays with orbital mirrors or
crashing (smaller) asteroids into the ice.
Not done yet. Both Venus and Mars
lack a substantial magnetic
field, a problem for two
reasons. The first, as I’ve
explained before, is that
a magnetic field protects
surface inhabitants from
space radiation.
The second is
that the magnetic
field
helps keep
the planet’s
atmosphere
from being
stripped away by
the solar wind.
While we don’t
know exactly
why Mars lost
its atmosphere
or how much it
had to start with
(a probe is being
launched in 2013 to shed light on
these stumpers), the absence of a magnetic
field is a likely culprit and would
probably put the kibosh on its retaining
an atmosphere in the future. You may
object that Venus seems to be hanging on
to its atmosphere just fine, but don’t be
deceived—it’s shedding atmosphere, too.
It just has so much more to lose that it’ll
take a long time to reach Earth’s atmospheric
density.
In short, moving planets doesn’t seem
like a cost-effective use of federal funds,
although given some of the other ventures
we’re pouring tax dollars into, it’s not
something I’d completely rule out. (Note
that NASA did raise the possibility in a
press release dated April 1.) I hate to be
one of those use-sunscreen type of guys,
but the most economical thing to do is
quit scuzzing up the planet we’ve got.
Comments, questions? Take it up with Cecil on the Straight Dope Message Board, StraightDope.com, or write him at the Chicago Reader, 11 E. Illinois, Chicago 60611.