Borehole Cluster

The **Borehole Cluster** is a landmark in *Alpha Centauri*.

## Description

In one area, the colonists found unmistakable evidence of past engineering of Planet's surface: three thermal boreholes drilled through Planet's crust, about 200 miles apart. The boreholes were somehow being maintained against local geological forces, and remained useful despite the thousands (or even millions) of years since their construction.

## Interlude

"What is it? Report!" You bark the orders with all the patience of one
whose days have become an endless stream of budgets, battlefield analyses,
and supply requisitions.

"We've completed our investigation of the Borehole Cluster, $TITLE0."

highlights."
The young engineer's eyes are shining as he hands over the datapad.
"It's an amazing feat of engineering, $TITLE0. A shaft has been drilled
all the way through the planet's crust, right down to the magma. The
mineral resources are right there for the taking, and the energy tap
from the heat could be enough to power our largest turbine plant!"
"Excellent. Have you discovered how they protect against meltdown,
and how they extract the minerals?"
"It's all in the report, $TITLE0." The young man looks proud, but
then his face changes. "There is one disturbing thing, $TITLE0."
"Yes?" You're already thinking of how this technology can be
incorporated into your plans for Planetary domination; "disturbing"
is not a word you wanted to hear.
"Well, $TITLE0, our dating techniques show it to be only slightly
newer than the nearby monoliths and artifacts. And the construction
materials used in the borehole perimeter can't be duplicated."
datapads and look up. The young engineer's demeanor is that of one who
is about to deliver very discomfiting news.
"Well, spit it out! What's wrong?"
"It's not exactly [wrong], $TITLE0. It's just that ... well, the
boreholes are similar to the type we've created ourselves: a direct
tunnel to the magma core of the planet, tapping into a great deal of
energy with very little entropic loss through the use of induction
coils and so forth."
"Yes, yes." You're familiar with the theory, and even the
practice. "What else?"
"Well, $TITLE0, this structure was definitely not created by
an Earth faction. Our dating techniques show it to be only slightly
newer than the nearby monoliths and artifacts."
"Interesting." That means that the alien culture that once lived
on Planet had reached a greater level of technological advancement
than had previously been confirmed, though it had of course been suspected.
"That's not all, $TITLE0." The young man looks highly uncomfortable.
Finally he blurts, "It's the construction materials used in the
borehole perimeter. We can't duplicate them."

Your eyes narrow. "Why?"

He gulps. "Well, $TITLE0, the metals used are not native to
Planet. Their composition includes many elements not found anywhere,
at least so far, in Planet's crust."

You goggle at the young engineer, astounded at the implications:
The race that left behind these monoliths, these artifacts ... they
must have come from the stars, just as humanity did. Were they
defeated by Planet's biological defenses? Did they leave? And if
they left ... might they ever come back?