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# 2023-12-17 - Shepherd Moons by Jerry Oltion

(IMG) Illustrated by Eldar Zakirov

The mood in the control room was tense. When everything depends on
the next hour or so, people grow quiet and focused. In a little less
than an hour, the DART spacecraft would arrive at the asteroid
Didymos, and all their effort would go out in a final blaze of glory.
Priya Joshi and her partner in crime--and in practically everything
else--Mark Anderson, shared a monitor at the end of the back row.
They weren't directly part of the mission, but as astronauts with
extensive EVA training and experience navigating spacecraft, they
were there to observe and learn and help if they could. Plus Priya
was on NASA's asteroid exploration team, an as-yet theoretical
sub-group of astronauts who might someday actually venture out to one
of the Solar System's flying rocks, and this was her chance to see
one up close. Really close.

It wasn't every day that NASA whacked an asteroid with a half-ton
space probe. DART was designed to test how much influence an impact
would have on the asteroid's orbit, but it was also proof of concept
for much more ambitious missions to follow, some of which might be
crewed depending upon what they discovered tonight. Didymos was an
Earth-crossing asteroid with a two-year period, relatively easy to
reach and relatively easy to return from after an extended stay. If
NASA ever sent a mission out there, Priya planned to be on board.

The mission clock ticked over to 6:30. Forty-four minutes to impact.
Didymos was a bright speck in the center of the field, still too
small to show a disk. But the probe was approaching at over four
miles per second, and as they watched, a dimmer speck separated from
the bright one. Dimorphos, Didymus's tiny moon. That was the actual
target. DART would strike it head on as it swung around in its orbit,
slowing it down by a smidgen, enough for telescopes on Earth to
detect the difference in its period after a few more orbits. And that
sudden slowdown would change the orbit of the larger companion by an
even smaller smidgen. Not enough to matter, but it was a
proof-of-concept mission, a demonstration that we could alter the
orbit of an asteroid if we needed to.

A cheer filled the room as the two bright dots separated. "Right on
schedule," Mark said. So far the mission was going nominally. It was
entirely automated at this point, with the probe thirty-six
light-seconds away, so if anything went wrong, there would be little
the controllers could do to correct it.

"It'll be switching guidance from Didymos to Dimorphos," Priya said.
And as she spoke, the view gave a little jerk. "That was the thruster."

The mission communicator a few stations down the row said, "The probe
has achieved a navigation lock on Dimorphos. All systems are 'go.'
Forty-one minutes to impact."

Priya said, "That means the probe is... almost exactly ten thousand
miles out."

Mark laughed. "Stop showing off!"

Priya felt herself blush. "The numbers are easy. Four miles per
second, sixty seconds in a minute, forty-one minutes."

Mark said, "Four miles per second sounds fast, but it's less than
orbital speed. The ISS is going faster."

"But the ISS isn't going to smack into an asteroid."

"I hope not," Mark said. "I'm going up next year."

She fist-bumped him. "To a great mission." She'd been up once, three
years ago, but wasn't even on the schedule again.

"You'll get another shot at it," he said.

Priya just shrugged. To be honest, another tour on the ISS wasn't
high on her list of priorities. She wanted the Moon, or an asteroid
like Didymos, or even Mars. To actually go somewhere, see something
new, accomplish something nobody had done before.

The two specks drew apart on the monitor as the probe closed in. Mark
said, "I read somewhere that the number of Earth-grazing asteroids
that are binary is way higher than the number of binaries out in the
main asteroid belt. Weird statistic."

Priya said, "It's the YORP effect. Sunlight on a rotating body makes
it spin faster, and it eventually breaks apart. Sunlight is stronger
on near-Earth asteroids than on main belt asteroids."

Mark laughed. "I was just going to guess that."

"Sure you were."

Priya took a sip of coffee and kept the mug in her hand for warmth.
She had become shivering cold in the last few minutes.

They watched the asteroids draw apart, Didymos finally becoming a
disk rather than just a point of light. It was roughly spherical,
with boulders and depressions more or less at random.

Dimorphos was much smaller, only five hundred feet, a fifth the size
of Didymos, so they didn't see detail until just a couple minutes
before impact. When they did, all that stood out was just a bright
spot on a surprisingly smooth, round surface.

"That's weird," Priya said. "It's more spherical than Didymos. You'd
expect the smaller one to be more ragged. Less gravity to pull things
together."

It was growing fast now. Didymos slid off to the side of the screen,
leaving Dimorphos dead center. The bright spot began to take on
shape, but that shape was perfectly round. Round with a blister dead
center. Sunlight angling in from the side made it obvious that they
were looking at a dome. A dome with round ports, dish antennae, and
angled black solar panels.

Voices raised all around the control room. "What the hell! That's
artificial! Who put that there?"

Priya said, "Abort! Abort! Oh, shit." She set her coffee mug down
hard on the desk, sloshing it, but didn't look down. She couldn't
tear her eyes away. The probe sailed straight onward, the abort
signal crawling along after it at the speed of light, if one had been
sent at all. Nor could the thrusters move the probe far enough in the
few seconds left even if the signal had been instantaneous.

The guidance system did an impeccable job: The probe struck dead
square in the center of the dish antenna mounted atop the domed
outpost.

The video winked out upon impact, but DART had deployed a cubesat ten
days earlier that had drifted behind to watch the results. LICIA got
clear video of the expanding debris cloud.

Shrapnel erupted outward from the surface, blasting into space in a
tight cone--aimed directly at LICIA. There was just time to make out
some of the tumbling girders and twisted metal panels before LICIA
ran into the debris cloud and the signal stopped.

The control room erupted in pandemonium. Among the dozen other
voices, Priya said to Mark, "The facility must have been dug into the
asteroid a ways. If it was completely on the surface, the explosion
would have blown everything out sideways. But the ejecta mostly came
straight back along the incoming path, which means it was directed
like rocket exhaust. My guess is that there were at least a dozen
basement levels."

Greg, the tech at the station next to her nodded. "It reminds me of
the 9/11 attacks on the World Trade Center. The planes just
disappeared into the buildings for a second or two before the
explosions. The force was all outward, and it came from deep inside."

Priya had been in grade school when that happened, but she remembered
the video as if it had been yesterday. "Yeah," she said, "The
structure was mostly empty space. And that's what it looks like we
have here. The explosion didn't really take off until DART hit bottom."

Mark said, "That implies habitation. If it was a robotic
installation, there wouldn't be any need for empty space."

"I didn't see any bodies in the debris," Greg said.

"It's hard to tell," Mark said, "but it doesn't look like there was
atmosphere in there. The debris was all solid stuff. Hardware."

"And rock, there at the end," said Priya. She tapped the video slider
on her monitor and dragged it back a quarter inch, replaying the
impact and its aftermath. Amid the metal debris, several obvious
chunks of ragged asteroid material also flew out. Priya said, "That's
from the ground floor."

It's amazing what you can learn by watching something be destroyed,
she thought. They were like physicists examining particle tracks in
an atom smasher, deducing what had to have created the patterns they
saw.

"Who the hell could have put that there?" someone down the row asked.
"And why?"

"Elon?" Mark said.

Greg said, "Not likely. Something like this would have taken a major
launch effort. He'd never have been able to keep it secret."

"China, then?" Priya said.

"North Korea," someone else said, and everyone laughed. But it was a
hollow laugh. Someone had obviously put an outpost on Dimorphos, and
the only good reason for doing that was the same reason for the DART
mission: to nudge the binary pair into a different orbit. But if they
were doing it in secret, then presumably they intended to shift it
onto a course that would impact Earth.

* * *

Priya was in the Astronaut Office first thing in the morning. "I
volunteer for the mission," she said.

To his credit, the director didn't ask "What mission?" He just said,
"We're not even close to assigning a crew yet."

"I know that. But when you do, I'm your best candidate. It's a
two-year trip out and back, so supplies are going to be our biggest
concern. I weigh a hundred and ten pounds and can thrive on a twelve
hundred calorie diet. Probably less in freefall. And I'm already in
the asteroid rendezvous group. And my Ph.D. thesis was on the search
for extraterrestrial intelligence."

He raised his eyebrows. "You think that was an ET outpost?"

"When you've eliminated the impossible, whatever's left..."

"Yeah, right. I think we're far from proving that someone from Earth
couldn't have set that up. But yes, you're on the short list. Because
we're probably going out there no matter who turns out to be the
culprit."

Priya thanked him and let herself out, nearly bumping into Mark in
the hallway. "Beat you to it," she said.

Mark laughed. "We'll see how much that matters when the time comes. I
get the feeling there's going to be a lot of money thrown at this one."

"Yeah, maybe so. Good luck to both of us, then." Priya gave him a
quick hug. But she knew it was a one-person mission, and she knew who
was going.

* * *

In the following days, astronomers turned practically every telescope
on Earth--and off it--on Didymos and its mysterious moon, but saw
nothing remarkable. Radar picked up sparkles of reflection from the
debris still moving away from the explosion, but no motion on the
surface.

Nobody radioed for rescue, and nobody on Earth claimed responsibility
for the installation. Dimorphos's orbit had shortened by about a
hundred and thirty seconds, nearly twice the predicted amount,
presumably due to the focusing effect on the ejecta plume.

At least there wasn't an advancing fleet of vengeful aliens. But as
the days drew on without answers, speculation ran rampant on the
internet. It was the Russians. It was Martians. It was Satan.

It was a leftover spacecraft from the fleet that had seeded the Earth
with life billions of years ago.

And of course it was responsible for COVID-19, global warming (which
was nonetheless a myth), and inflation.

Then astronomers noticed that something had detached from another
Earth-grazing asteroid about forty million miles away and was heading
toward Didymos. Under power. There was no visible rocket exhaust, but
the thing was accelerating continuously at 2.5 gees. In fourteen
hours it had covered half the distance, then began decelerating at
the same 2.5 gees.

If there had been fuel involved, the acceleration would have
increased as the mass of the spacecraft decreased. Maybe the
aliens--for nobody seriously doubted anyone else was behind it
now--had an upper limit that they could withstand and had throttled
down as their mass decreased. Or maybe they were using entirely
different technology.

Maybe they were from Jupiter, which maybe not coincidentally had a
surface gravity of 2.5 gees. Or maybe they just wanted to make us
think they were from Jupiter.

Maybe, maybe, maybe. Nobody knew anything for sure.

Debate raged over whether to contact the aliens or not, but it was a
moot point. Practically every nation made a clandestine attempt, but
none were successful. Either the aliens weren't listening or weren't
interested in responding.

There had already been a follow-up mission in the works. Called Hera,
it was the second half of AIDA, the "Asteroid Impact and Deflection
Assessment" program that Priya had been involved in for years. Hera
was due to launch in 2024 and rendezvous with Didymos in late 2026 or
early 2027.

The only way to speed up an interplanetary transfer is with sheer
power. If you've got the thrust for it you can shoot straight for
your target and get there in weeks rather than months, but it takes a
phenomenal amount of fuel. Nobody on Earth had a space drive that
could keep up 2.5 gees of thrust for over a day, but SpaceX had a
rocket they once called the Big Falcon Rocket, later renamed
"Starship" when people realized what BFR really stood for, and it had
already made several successful flights. It was designed to carry
people to the Moon and to Mars; NASA suggested putting the Hera probe
on a stripped-down Starship and sending it out to Didymos at top
speed. It would still take several months, and the rendezvous would
be at the far point in Didymos's orbit, and the probe couldn't go
into orbit around the asteroid as originally planned, but it would
get there years earlier and could at least send photos of what the
aliens were up to.

And humanity collectively shivered in fear as they waited. There were
over a dozen binary Earth-grazing asteroids, and it was a safe bet
that every one of them had an alien outpost. None of them were on
orbits that would bring them truly close to Earth within the next
century or more, but with engines capable of keeping up 2.5 gees of
thrust indefinitely, it wouldn't take long to alter one's orbit until
it was on a collision course.

Priya lobbied for a crewed mission to follow, no matter what Hera
discovered. Surprisingly, NASA agreed, perhaps worrying that SpaceX
would do it on their own if they didn't. Or China. Or Russia. Or
North Korea. It was imperative that the U.S. be first.

But of course that meant asking Congress for the money.

* * *

The hearing was a joke. But after the midterm elections, Congress
itself was a joke. The hearing started out simple enough, with
questions like "Why can't we just aim the James Webb telescope at
it?" (Followed by the inevitable grumble: "We spent enough on the
damned thing, it ought to be useful for something.")

Priya, as the spearhead behind the mission--and because
Congresspeople liked being photographed with astronauts--was NASA's
representative. She answered with the truthful observation that at
Dimorphos's distance, even the Webb couldn't see the level of detail
they needed.

What could we possibly do with a manned mission that we couldn't do
with robots? Adapt to what we find there.

What do you expect to find? We don't know. That's why we need to go
look.

How do you propose to stop them once you get there?

And so on. It was clear from the start that the conservatives wanted
someone to blame and someone to bomb, while the liberals wanted to
convene a panel of experts who would study the situation for a decade
and make a recommendation. And of course there were the grandstanders
who asked brilliant questions like "Why didn't we know about this
beforehand?"

To which Priya merely replied, "Congressional budget cuts," and let
the silence linger.

Then the representative whom Priya had come to think of as the
Honorable Stupid Son of a Bitch from the State of Ignorance asked,
"How many men does NASA propose to send?"

Priya said, "One. And it'll be a woman. Me."

"You," he said flatly. "A little slip of a brown girl."

She bit her tongue. Took a deep breath. "An experienced astronaut who
has extensively studied both extraterrestrial contact and asteroids.
And who can live on twelve hundred calories a day. Which is a vital
consideration for a mission of this duration," she added for those
who hadn't been paying attention earlier.

Congressman Stupid cleared his throat and said, "No offense, Miss
Gupta, but if we approve this boondoggle, we'll be sending a man up
there. A white man."

A murmur swept through the chamber, but there was no bang of the
gavel, no outcry of protest. So Priya said, "No offense, Congressman,
but if you can say that and expect to be reelected, then we are all
well and truly screwed, alien invasion or no."

* * *

Mark cooked dinner for her that night. The TV was off. Neither of
them wanted to hear the outcry from the conservatives accusing her of
disrespect for the government that they showed no respect for,
either, nor from the religious nuts who were already accusing her of
making a pact with the devil, nor from the liberals who wanted to
spend the money on vaccines and food for starving nations. Priya
didn't even want to think about it at the moment, but she couldn't
put it out of her mind.

Halfway through the meal, a delightful shrimp scampi on linguini with
garlic toast on the side ("Good thing we're both eating this or
there'd be no smooching you for a week."), she said, "You know, I'm
beginning to wonder if I want to go out there after all. All the
evidence seems to point toward hostile aliens bent on wiping out
humanity before we can get a foothold outside the Solar System. What
could I possibly accomplish besides setting them off even more than
we have already?"

"You could make contact," Mark said. "We need to do that whether
they're hostile or benevolent. We need to find out what they're doing
and why."

"They're moving asteroids around. That much is obvious. And as for
why, I think that's pretty obvious, too. Why else are so many doubles
in Earth-crossing orbits?"

Mark considered that for a bite or two, then said, "Why do none of
them come closer than a couple of million miles? With no impacts in
the foreseeable future? If whoever's out there wanted to be able to
smack us down on a moment's notice, you'd think they'd keep one ready
to go."

"So you think they're just hanging out to watch us and using the
asteroids to sweep in for a closer look every now and then?"

"Maybe. Or maybe they're keeping the asteroids away. Maybe they're
watching over us, not just watching us."

"That would be nice if it were true. But why don't they answer our
hail now that we know they're there?"

He took a sip of wine. "Could be a test. We have to be able to reach
them before they'll respond."

She snorted. "Oh, we reached them all right. You'd think that would
have been enough."

"You know what I mean. Columbus didn't reach the new world by sending
a message in a bottle. He had to come here himself."

"And live to tell the tale."

"You'll make it."

"Or you will. Senator Shithead isn't the only misogynist racist in
Congress. I probably killed my chance of a mission anywhere, much
less to Dimorphos."

Mark shook his head. "Nonsense. You're the most qualified, most
logical choice. Of course you'll go."

* * *

But when the mission was approved and the crew announced, it was
Mark's name at the top of the list, with Priya as backup.

She spent a day sulking, and another day feeling guiltily relieved,
then she put aside her anger and her grief and her anxiety and helped
Mark train for the flight. He insisted that she train right alongside
him, because something could happen to him at the last moment and she
could wind up going after all.

Whoever went would be riding in a modified Starship crew module. The
thing was as big as a bus, with plenty of room for a couple dozen
people if they were just going to the Moon and back, but for the
extended trip to Dimorphos, every cubic foot of space would be taken
up with food and oxygen and supplies to keep even a single person
alive. The margin was tight with Mark's extra mass, but doable. With
Priya it would be a breeze.

The Hera mission swept outward. The faltering economy improved as
people, convinced humanity was doomed, spent their savings on sports
cars, boats, vacations, and lots and lots of survivalist supplies.
Priya wryly noted that there was enough high-velocity lead being
stockpiled in underground bunkers to deflect Didymos if it was all
fired at the asteroid. She got hate mail and death threats for that,
but she had been getting those for months now.

Hera reached the asteroid and sent back a flyby image of a dome under
construction that looked just like the one that DART had smashed.
Little creatures or robots or something dotted the surface of the
asteroid, but they were only a foot or so long, too small to show up
well in the images. Were they truly space aliens, lifeforms that
lived in vacuum? Nobody knew. But it was clear they were rebuilding
their outpost.

Not long afterward, astronomers noticed something odd: Dimorphos
acquired a wobble in its orbit. It was speeding up as it swung around
in the direction approaching Earth, and slowing down on the other
side, falling closer to Didymos when it was around behind it and
rising up higher when it was on the Earth-facing side. Then they
realized it wasn't Dimorphos's orbit that was changing, but Didymos
itself, the big asteroid. But it was moving onto a path that took it
even farther from Earth than before. The aliens were moving it away
from the Earth, not toward it.

The difference was only a few thousand miles; an almost insignificant
amount on the scale of the Solar System, but it clearly meant
something. But what? A warning? A peace offering? A thumbed nose?

"They're probably testing their repairs," Priya said to an
interviewer who asked her opinion.

Of course the news story twisted her words, proclaiming "Aliens test
asteroid-moving ability in preparation for attack on Earth!"

The Starship project proceeded apace. Fuel flights rocketed into
orbit, stockpiling propellant for the long burn. The crew module was
loaded with supplies, including thousands of hours of movies,
thousands of digital books, and thousands of hours of music, in part
to trade with the aliens if cultural exchange was possible, but
mostly to keep the passenger sane on the long way out there.

And three days before launch, Mark developed vertigo.

"You're what?" Priya demanded when he told her. They were both in his
bed, where she'd given him a hero's send-off for most of the night.

"I'm dizzy."

She laughed. "You're shagged out," she said.

"No, I mean it. Everything is swirling around." He tried to sit up,
but twisted around and fell heavily back into the bed. Then he turned
his head sideways and threw up.

"Don't choke!" Priya pushed him hard over so he was on his side.
"Breathe out first!"

He coughed, gasped, coughed, then took a deep breath. "Gah. Get a
towel."

She grabbed two from the bathroom, threw one over his mess, and
handed him the other.

"Maybe it's food poisoning," she said. They had been eating well in
his last few days on Earth.

"Maybe." He wiped his face and tried again to sit up. She helped him
upright, but he had to close his eyes to keep from throwing up again.
"Everything's swirling around," he said. "Fast. Teacup-ride fast."

"That's not good."

And indeed it wasn't. When they finally got him to the flight
surgeon, a half-full barf bag and many dry heaves later, the flight
surgeon diagnosed a swollen inner ear. "I hate to break it to you,
bud, but you're not flying in that condition."

"How long before the swelling goes down?" Mark asked.

"A week, maybe two. But that's not the real issue. Once this sort of
thing develops, you never know when it's going to happen again. And
the natural rush of fluid to the head in microgravity will just make
it worse."

"So my career is shot."

"Maybe not. There are medications you can take. Surgery if that
doesn't work. Alan Shepard beat it and made it back into space, and
you can, too. But not in three days time."

Mark turned--carefully--to Priya. "See," he said, laughing softly. "I
told you it'd be you."

"Not like this!" she said. "I don't want to take your place!"

But there was little choice. Mark was grounded, and she was next in
line.

The death threats became more serious. Her entire apartment building
had to be evacuated after three separate drive-by shootings. She had
to bunk in the crew quarters at NASA. Even Mark had to stay there, as
the internet filled with conspiracy theories that he had "chickened
out and passed the torch to his n--"

"I sometimes wonder if we'd be better off with alien overlords," he
said sadly on the eve of her departure.

"Maybe I'll ask them to invade," Priya said. "If they aren't already
planning to."

* * *

Launch day. Priya rode the gantry elevator to the top, transferred
into the Starship--named simply and appropriately Envoy--and strapped
in. Practiced routine took over, and in what seemed like an eyeblink,
the thirty-three Raptor engines lit, and she felt the entire stack
shove her back into her couch. The low cloud deck flashed past, the
sky turned dark, and within minutes she was in orbit, catching up
with the fuel depot.

Refueling took the better part of a day, assisted by the crew of a
regular Falcon mission. And in one more twist of the whirlwind, Priya
lit the engines again and was off.

Didymos and Dimorphos were swinging back around toward Earth on their
two-year orbit.

Priya's velocity and their velocity combined to close the distance.
This wasn't a transfer path, where she would sneak up on her target
and slowly match course with it. This was going to be like a carrier
landing, full thrust again at the end and hope her navigation was
spot on.

When the outward burn stopped, she was moving at well over escape
velocity. Not as fast as Hera on its flyby trajectory, but plenty
fast. The Moon was visibly moving away, off to the side.

Earth was directly behind her, seen only in the aft camera view, but
receding like a marble dropped down a well.

She reported her condition as nominal and told mission control she
was going to get a couple of hours of sleep. She put the radio in
standby, turned off the internal cameras, unbuckled her safety
harness, stripped out of her flight suit, and set out to find the
nuclear bomb.

There had to be one. Probably just a suitcase nuke, only one or two
kilotons yield, but that would be plenty to spoil Priya's day if some
hothead in the Pentagon decided to set it off. And who knew what the
aliens would do in response? They didn't seem to have cared much
about a kinetic impact, but Priya guessed a nuclear weapon might just
piss them off enough to respond.

It took her four hours to find it. It was in the equipment bay,
disguised as an oxygen tank.

She only discovered it when she realized that this tank wasn't
actually plumbed into anything. It just had a wiring harness leading
to a connector spliced into the main bundle.

"Cut the blue wire, or the red wire?" she asked quietly as she
studied it. How would she have wired the thing if she had placed it
here?

She certainly wouldn't have set it to explode during a power failure.
So she reached out and pulled the connector apart.

There was no digital timer on the side of the tank. No androgynous
voice calmly counting down her last few seconds. Even so, her heart
pounded loud in her chest, and she could hear the blood whooshing in
her ears. But aside from that and the ever-present air circulation
fans that ran constantly on any crewed spacecraft, the ship was silent.

She had to rummage in the tool chest for a wrench to free the bomb
from its bay, then wrestle it though the cabin to the airlock. It was
about the size of a large beach ball, and she had a bad moment when
it looked like the airlock door was an inch too small for it, but the
nuke wasn't perfectly spherical. In the right orientation it fit in
the lock with room to spare.

Which was a good thing, because the lock didn't have automatic
controls. She had to suit up again and climb in with the bomb, then
cycle the lock and shove the bomb out into space. She gave it a good
kick with both feet, hanging onto the airlock grab rails as she did,
and was happy to see it tumble away at a pretty good clip. "Okay, so
I just violated the Outer Space Treaty on nuclear weapons," she said.
"There were mitigating circumstances." Then she closed the airlock
and went back inside.

* * *

Nobody mentioned it, of course. It was possible nobody even knew,
wouldn't know until they tried to power up their ace in the hole and
discovered it unresponsive.

Weeks passed. Mark's condition improved, as Priya knew it would.
Whatever he had done to give her the mission, he wouldn't have done
himself permanent harm. In fact, she bet he hadn't done himself any
harm at all. The flight surgeon had to have been in on it; all Mark
had needed to do was swallow an emetic a few minutes before "waking
up" and declaring himself dizzy, and that was that.

He became the capsule communicator, her link with the ground. They
pushed the limit on personal conversation amid the instrument checks
and daily briefings. As the distance between Priya and Earth grew,
the light-speed lag grew with it until they were waiting half a
minute for replies, then a full minute, then two. Priya listened to
Mark's choice in music, watched his movies, read his books, ate his
food, marveling at how well he had anticipated her tastes.

He must have studied her apartment with a magnifying glass to know
her so well. If she ever doubted that he had thrown over his position
on the flight for her, the dozens of bags of Peppermint Patties
clinched it. He didn't even like them.

And Didymos finally rose out of the darkness. Another long burn of
the main engines, a minor course correction, another shorter burn,
and the familiar rock face drifted slowly up to meet her. At first
Dimorphos wasn't visible, but as she drew closer it swung around from
behind Didymos, a smooth ball one-fifth the size of its larger
companion.

She was suited up and strapped into her command couch. If she
crash-landed and split open the crew cabin, she would at least have
air and time enough to investigate the dome, which was once again
complete, or so it looked in the telescope view.

But the navigation computer performed flawlessly, matching her
velocity with the tiny moon and bringing the ship to rest less than
its own length away.

"I'm here," she said simply, knowing it would take almost a minute
for the news to reach Earth and another minute for Mark's response to
return. "Still no response from the inhabitants.

I'm blinking my navigation beacon in prime numbers, but I don't see
any lights on the dome. It looks like they've finished it. No sign of
our impact. If we left a crater, the dome has filled it completely.
Or maybe they--"

"We copy your arrival," Mark said. "Congratulations on being the
first human being to reach an asteroid. Hold station for a few
minutes and see if the dome builders respond. Try blinking your
navigation beacon in prime numbers."

Priya laughed. Her voice came out ragged between panting breaths, and
her heart felt like it was going to tear itself out of her chest. Now
was the time the aliens would blast her into atoms if they were going
to.

"No response," she said, not sure whether it was a report or a prayer.

The ship was drifting a bit. She could match velocity and hover a
while longer, but she hadn't come out here to hover. "I'm going to
land it," she said.

"Oh, you already thought of that," Mark said. "And no response.
Somehow I'm not surprised."

She didn't so much land on Dimorphos as dock with it. The asteroid's
gravity was almost negligible. She could probably have drifted up
alongside and simply let the ship come to rest against it, except the
spacecraft still had mass and she could shear off a thruster or an
antenna before it stopped. So she swung it around and aimed the
landing legs at the surface and brought it in slowly with gentle
nudges of the maneuvering thrusters. Her windows all faced sideways
and upward, so she watched the camera view. It felt like backing up a
Prius.

The asteroid surface looked like a freshly groomed construction site,
which was pretty much what it was. Small, shiny metal spider-like
vehicles about the size of house cats crawled across the ground,
scooping up loose regolith and carrying it to the hopper of what was
probably a furnace that smelted the stuff into its metallic
components. A pile of slag in back of the furnace confirmed her guess
and somehow disappointed her, too. Shouldn't advanced alien
technology be well beyond creating slag piles? Other spiders took
foot-long ingots of metal from the furnace and carried them to the
dome, where they disappeared into a tiny port that might have been an
airlock or might have been a simple hole in the side of it. The dome
that DART had destroyed hadn't been full of air; there was no reason
to suppose this one was, either.

The spiderbots didn't seem to notice her approach. As she brought the
ship in, one of them crept along directly beneath it. She slowed her
descent until it had cleared the landing site, then accelerated
again. She needed at least a couple of feet per second of impact
velocity to activate the tethers.

Of course at the last moment the spiderbot swerved back directly
beneath one of the legs, and the docking probe speared it like a ripe
tomato. Then the probe sensed the hard surface and fired its
explosive charge, driving the two-foot spike right on through the
spiderbot like a spear gun through a fish.

"Crap," Priya muttered. "Here we go again with the unintended
destruction of alien property." But three green lights winked on in
the navigation display. "At least we've got positive lock on the
tethers." She felt a bump as the reels pulled the landing pads tight
against the rock.

She tried again with the navigation beacon and called a general hail
on the radio, but there was still no answer. Mark said, "Looks good
for landing."

She tapped at the screen. "Shutting down navigation," she said.
"Inertial guidance off.

Thrusters disarmed. Fuel pumps off. Accelerometer--oh, wait, let me
get a reading. Ha! Five point one times ten to the minus sixth, just
as we calculated. Are we good or what?" She continued down her
checklist, and only after she'd finished the shutdown sequence did
she realize she'd forgotten the history quote.

"Copy you down," Mark said.

"Right. Um, yes, the Envoy has landed." Brilliant.

She looked out the window toward the dome, narrating what she saw
even though the cameras were seeing and recording even more than she
could from her single vantage point. "Still no sign of awareness that
I'm here. I see several multi-legged vehicles that I assume are
construction robots crawling slowly from place to place. They don't
seem concerned that I just speared one with a landing spike. Sunlight
is glinting off the side of the dome. It's fairly bright, but the
dome doesn't look polished. Just shiny, like aluminum or steel that's
been freshly milled. No lights. I do see several round outlines that
might be ports or windows or something, but they're the same shiny
surface as the rest of it. I see one rectangle about the shape of a
door that's solid black, like an opening to the inside. I assume
that's the entrance."

She took a deep breath. Her heart rate had slowed down a little with
the routine of landing, but it was edging upward again. "I don't
really see any point in waiting. I'm going to go check it out."
Before I lose my nerve, she didn't say, but she was certainly feeling
it. She thought she'd left her anxiety far behind, but now that she
was here, literally only feet away from an alien artifact--and quite
possibly aliens themselves--she could see swirling tracers in her
vision and hear her breath coming ragged in her earphones.

"We're getting infrared from the black rectangle," Mark said. "But
whether that's heat from the interior or just absorbed sunlight, we
can't tell. It's black-body radiation, no spectral signature."

"We'll find out soon enough what it is," Priya said.

She unbuckled and twisted around to the cargo lockers. Her suit had
two video cameras built in, but she also picked up her phone, which
she kept charged for recording her personal journal. And from down in
the bottom of locker twenty-six she pulled out the cardboard
disposable camera. Thirty-six exposures on good old Kodachrome film.
Even if the aliens pulled a Jodi Foster on her and wiped out her
digital data, there was at least a chance that they wouldn't know
about photographic film, nor how to fog it.

Of course winding the little bugger with spacesuit gloves could be an
exercise in frustration, but she'd practiced it a dozen times back on
Earth and managed to make it work.

She tucked the phone and camera into leg pockets. "Okay," she said,
disconnecting her suit from the ship's air supply and pulling herself
up to the docking hatch atop the capsule. "I've got eight hours of
oxygen if I don't hyperventilate. I've got cameras. Radio is working.
I'm as ready as I'll ever be." She twisted the handle and pulled the
hatch inward. Pulled herself upward into the airlock.

Mark said, "The olive branch! Don't forget the olive branch!"

"Oh, holy... right. The olive branch." Priya pushed herself back down
into the cargo bay and opened locker twenty-six again, rummaged
around until she found the freeze-dried peace offering in its
vacuum-sealed bag. It looked surprisingly good after its months in
storage, but Priya wondered how much of that was the fact that this
was the only sign of life on board other than herself. She swallowed
a lump in her throat and said, "Olive branch, check." It was too big
for a pocket, so she tucked it under one of the suit's waist straps.

She pulled herself back up into the airlock and tugged the hatch
closed after her. "Up" being a more or less visual referent than
anything else. She opened the valve that let the air out, feeling her
pressure suit stiffen as it did. Her breathing seemed to become even
louder than before, but she hoped that was only because she'd lost
the ambient sound from the ship now that there was no air to transmit
it.

She clipped the end of her tether to her waist, then popped the outer
hatch and swung it outward, following it until she was half out of
the circular ring. This was more of a spacewalk than a surface
expedition. There would be no walking over to the dome. The first
step would launch her into orbit, or possibly escape velocity.

"Heart rate's one-twenty," Mark said. "Take some deep breaths."

He was reacting to her telemetry while she was still in the airlock.
She was up to one-fifty now. Deep breaths were probably a good idea.

She closed her eyes. Imagined sitting on a couch with a fuzzy kitten
in her lap. Purring.

Back down to one-thirty. Okay, that was probably as good as it was
going to get. On down the side of the ship, handhold over handhold.
It was a long ways down. She reached the ground and planted her feet
on it, holding herself down with both hands on the rung at waist
height, and this time she remembered to say, "We come in peace, for
all mankind." A stolen phrase, but there was nothing more appropriate
to say at the moment. She just hoped any aliens listening understood
what she meant, and cared.

She looked across the thirty feet or so that separated her from the
edge of the dome. The far side of the dome was actually beyond the
horizon. "I feel like Le Petit Prince here," she said. "The horizon
is about fifty feet away. And the Envoy is even bigger than a baobab."

She hooked a carabiner to a loop on the landing leg and slid her
tether into it, then pulled out several dozen feet of slack. She was
going to have to float across to the dome, and she wanted to make
sure she could pull herself back to the ship if she missed. From a
pocket she retrieved a magnet with a big T-handle. It wanted to pull
her around toward the bolts in the landing leg, but she turned away.

"Okay, here goes," she said, just as Mark said, "Amen to that."

She ignored him and positioned herself so her feet were up against
the landing leg and her body was horizontal to the ground, then very
gently extended her legs.

The robot-scraped regolith slid past just a few feet from her face,
coming closer. She had angled a little too steeply toward the ground.
She reached out and touched the surface with her fingertips, just
barely, and her angle changed by a few degrees. Too high now, but the
dome was tall enough that she would still hit it. Question was
whether there would be anything to grab when she did.

She watched her own distorted reflection grow larger. She reached
forward with the magnet and waited for it to pull her in, but instead
the magnet just hit the surface and bounced away. "Okay, not
magnetic," she said. She looked frantically for a handhold, a ridge,
a tunnel, anything she could grasp, and found a set of cris-crossing
flanges about half an inch high. Too small to get a good grip on with
her gloved hands, but enough to pinch between thumb and forefinger
and bring herself to a halt.

"I think these must be the tracks the spiderbots use to crawl around
on the surface," she said.

Very carefully, she pushed herself down the curve of the dome until
she was at the base of it, then she pulled herself around to the
black rectangle. It was so black she couldn't tell if it was a solid
thing or a hole into a pitch dark interior. It was about twice her
height, and just about half that in width. She reached out
tentatively and encountered resistance. Solid, then.

There was a yellowish loop sticking out about halfway along its long
axis, near the left edge.

She twisted around to get a good look at it.

"It's a door handle. With a thumb latch. Looks like brass." She
reached toward it with the magnet, and it didn't stick. "Not
magnetic. I bet it's brass." She laughed out loud. "It's a friggin'
brass door pull."

She grasped the handle and steadied herself, then banged on the door
with the magnet. It left no mark, and she heard no noise.

"All right, I'm going to try it." She pushed down on the thumb latch
and pulled on the handle, bracing herself against the side of the
dome as she did.

The door swung open. It was way thicker than a normal door, about a
quarter of its width.

Something about the dimensions triggered a memory, and she laughed
again. "It's a monolith.

From 2001: A Space Odyssey. The dimensions are one-four-nine, the
first three squares."

Mark said, "Copy your successful transfer. You're go for ingress if
you can find an entry point."

"I've found it, you numbskull," she muttered, but she was smiling.
Smiling and hyperventilating at the same time. Her suit flashed a
warning. Amber, not red. She held her breath until it went away.

Lights blinked on inside the dome, long glowing strips overhead
illuminating a corridor that led straight inward. "Okay, now we're
cooking," Priya said. "That's the first indication we've gotten that
they even know we're here."

Her vision was shot with tracers again. She had to take a few more
deep breaths, close her eyes, and envision an entire basket of
kittens. Then she pulled herself inside. Her tether trailed in after
her. Hmm. If the door closed behind her, it would snip the tether.

Not good. She wasn't eager to unclip it, but there was a convenient
loop just outside the door that seemed obviously made for the
purpose. So she unclipped, latched the tether to the loop, and pushed
her way on inward.

"You still receiving?" she asked. It was a long two minutes, but she
waited until Mark said, "Still copy you. Leave the door open, though."

"Ya think?" She pulled herself forward. The corridor was narrow
enough that she could put a hand on either side and pull herself along.

She was about thirty feet in when the light changed. She looked back
to see the door swing shut. She didn't hear the boom, nor feel it,
but she was pretty sure it had closed solidly.

"Mark, do you copy?"

Air rushed in. Her suit lost its rigidity. "If it's all the same to
you," she said, looking around at the bare metal walls, "I'm going to
leave my suit on."

She pushed onward. Mark didn't reply. Mission control was probably
going nuts about now, but Priya wasn't about to retreat to the ship
just to ease their anxiety. She was going to have to explore the dome
sometime, and she was already here, so they could just wait for her
report.

Or for the aliens to throw her body out the door.

The corridor ended in a large hemispherical room. It looked as empty
as a balloon, but as she pulled herself in and oriented herself to
stand upright against the flat metal floor, a column of light
flickered into being in the center and filled out to create a
hologram of--Santa Claus?

"You've got to be kidding," Priya said.

A soft, yet resonant voice said in her headphones, "Yes, actually, I
am. I'm hoping to calm you down. Your vital signs are borderline
dangerous."

"Tell me something I don't know."

Paintings and tapestries appeared on the walls. Furniture
materialized: A comfy couch, a low coffee table with magazines on it,
a kitchen table and chairs. A window opened up onto a forest with
birds and butterflies flitting about.

And the floor slowly became a floor. The asteroid was either under
thrust to somewhere or the alien had turned on artificial gravity. It
stopped at about a quarter normal, just enough to let her stand
upright, but not so much that she would be uncomfortable after her
long flight in zero gee.

"Does that help?" the red-suited hologram asked.

"A little," she admitted. "But I'm not exactly comfortable talking to
a childhood myth. Can you show me your true form?"

"My true form now is a tangle of circuitry and quantum gates. But in
the very distant past..."

Santa began to blur and shift, losing the beard and the garish red
coat to become a green-and-purple upright cylinder with a tuft of
yellow fronds waving like palm leaves from the top. Half a dozen
tentacles stuck out at seeming random from the central body, and
dozens of smaller tentacles held the base of it off the floor. It
might have been a tree, or a sea anemone, seen through a waterfall.

Priya gulped. She'd asked for it.

"Mind if I record this?" She held up her phone.

"Go ahead," said the alien. It held its tentacles out to the sides in
what might have been a welcome.

She activated the phone's video camera with the stylus nub on her
little finger, held it out aimed at the alien, and got out the
disposable camera with her other hand. There was no way to be sneaky
about it, so she just snapped three shots and tucked the camera back
in her pocket.

Then she said, "First off, just so we're clear, the impact that
destroyed your previous outpost was a mistake. We didn't know you
were here. We're sorry for the damage." She took the olive branch
from under her suit's waist strap and held it out. "This is a symbol
of peace among the people of Earth. We offer it in the hope that we
can coexist."

The alien's skin rippled slowly from bottom to top. Its voice
remained that of a patient old man. "Thank you. That's very kind, and
appreciated. We can definitely coexist." It glided forward on its
writhing foot tendrils and reached out with two of its upper
tentacles for the plastic packet, and Priya was surprised when the
packet left her hands and moved across the room with the hologram,
who placed it on a shelf that flickered into being as it approached.

The alien turned back to Priya and said, "You'll be wanting to know
if we're hostile or benevolent or what. We're mostly benevolent.
You've got a very dirty Solar System, with way too many asteroids in
way too many eccentric orbits. We've been redirecting them from
impact trajectories for about forty million years. Too late to save
your dinosaurs, and I have to apologize for Tunguska and Chelyabinsk,
but we've been pretty successful overall."

Priya felt a shiver run down her spine, but it was a shiver of
delight. "I knew it," she said.

"The number of binary asteroids in Earth-grazing orbits is way out of
line with the rest of the population. And they all miss Earth by
millions of miles. The odds of that happening by accident were almost
zero."

The alien rippled from the base upward again. "I was wondering when
someone would see that. You're right on the cusp of figuring out a
lot of things. When you do, there's a whole Universe waiting for you."

Priya's arm was growing tired even in the low gravity. She switched
the phone to her other hand. "What kind of universe are we looking
at? Are we talking Star Wars here, or Star Trek, or In the Ocean of
Night, or 2001, or Contact, or what?"

"Definitely 'or what.'" The alien waved its tendrils around. "The
distances involved are far too great for the creation of empires. If
faster-than-light travel is possible, we haven't figured it out yet.
Even trade is mostly done by information exchange. You're going to
get visitors every now and then, but not often, because the galaxy is
a big place and spacefaring species are few and far between. But
curiosity is probably intelligent life's strongest trait, so you'll
find young civilizations exploring their neighborhoods." The alien
paused and gave a little shiver.

"They're not always benign. The last ones through were about two
thousand years ago and were kind of jokesters. I reported them, and
they're probably still busting rocks on Ceti Alpha Five, but that
doesn't really help you a whole lot."

Two thousand years ago. Priya didn't know whether to laugh or cry.
What would happen when people heard about this on Earth? They
wouldn't believe her, not even if her recordings remained intact.
They couldn't afford to.

She said, "Mission control is probably going crazy by now. I've been
out of contact for what, ten minutes? Can you relay my video and
audio to my ship so they can listen in?"

The alien twisted its upper body left and right. "Sorry, no. I can
tell you anything you want to know, within reason, and you can record
anything I say, but I'm forbidden to broadcast directly to your
planet. Or to visit it. That seldom works out to anyone's advantage."

"So it's all on my shoulders and nobody is likely to believe me."

"Correct. Understand that we've done this many times before
throughout the Galaxy, and we've learned that as frustrating as this
may seem to you, it's the best way to avoid inadvertently damaging
your society. Merely discovering our existence is often fraught with
danger, but that much is unavoidable when you reach this stage in
your development."

"Could I at least go outside and tell them I'm all right?"

The alien rippled upward again. "If you wish. It will take a few
minutes to pump the air away."

Priya heard the thrum of the pump starting up.

"A pump?" she asked. "No force fields holding the air back?"

"Air is slippery. Pumps are more reliable."

"Why not an airlock, then?"

"Because the pump works well enough."

She nodded. Okay, aliens would have different ideas about what was
important and what wasn't. If this was the extent of the weirdness,
it was pretty insignificant.

"Sorry to put you out," she said. "I just don't want them to worry."

"I understand. It's actually very thoughtful of you."

She wanted to sit down, but the couch wasn't shaped right for her
spacesuit with its life-support backpack. So she settled for leaning
against the wall with her legs at an angle. Friction held her in
place, and she could loosen up her tight muscles for a minute or two,
at least.

"Do you have a name?" she asked. "I'm Priya."

"You're going to laugh. I'm--" a hissing sound with a pop and a click
at the end. "Ssspok."

She did laugh. "You're kidding me. Spock?"

"Unfortunately, yes. Mr. Rodenberry must have hit upon it
independently. There was nothing I could do about it." The alien made
a sort of sideways twist, the way a person might wring out a
washcloth. A shrug? "I can at least spell it without the 'c.'"

Priya could feel her pressure suit expanding, and the sound of the
vacuum pump was growing weaker. But she still had a couple of minutes.

"So, Spok without a 'c,' are you an artificial intelligence or an
uploaded personality or what?"

"I'm not an artificial intelligence. That would be very bad. A word
of advice: don't go there. There aren't many rules for emerging
civilizations, but that's one of them. If you create artificial
intelligence, we make you stop. Understood?"

Priya swallowed hard, then nodded. "Yeah, but again, I'm just me. If
you won't communicate directly, I can't promise anything about the
rest of the human race."

"Just make sure the word gets out. If the rest of your people refuse
to heed the warning, we'll shift to plan B."

Priya remembered the congressional hearing. "The world's being run by
idiots and billionaires," she said. "If you're counting on wisdom or
caution to win out, I think you're expecting too much of us at the
moment."

"It's surprising how motivating plan B can be once it's begun."

"I suppose you're not going to tell me what it is."

"Correct."

She could barely hear the pump now, and her suit felt about as tight
as it had on the way over. "Ready to blow the hatch?" she asked.

"Almost," said Spok. "Another minute."

She shifted her position against the wall. "So if you're not an
artificial intelligence, then what are you?"

"I'm a biological personality, recorded and held in storage to await
your arrival here."

"And you've been here forty million years?"

"Yes."

"Without going crazy."

"The subjective time has been much less than that. I've been inactive
for most of it. And there are copies of me on several other shepherd
asteroids, so we act as corrective feedback for one another."

"Is this something you can do with a human mind, too?"

Spok made the twisty shrug again. "In theory, yes. It would take some
calibration of the equipment. Your brains don't work the way mine
does. Or did. But that's undoubtedly one thing that will come with
further contact with other civilizations."

The gravity slowly diminished. Priya straightened up, holding onto
the doorframe to keep from drifting up to the top of the dome. "Hold
that thought. I'm going to go check in."

She pulled herself down the corridor to the black monolith door.

"Hold onto the handle," Spok said, his voice as strong in her
headphones as when she was in the room with him. "There will be
residual air that will blow outward."

"Right. Thanks." She grasped the handle--the same brass loop with
thumb latch as on the outside, and pushed the plunger. Sure enough,
the door swung open, drawing her out with it, and swung her around in
a tight arc. The door banged up against the side of the dome, and she
banged into it a moment later, clutching the handle for dear life.
Different ways of doing things, for sure. A cloud of dust blew
outward toward the horizon. She waited for it to dissipate, then
righted herself and clipped her tether to her suit.

"Houston, this is Priya. I'm outside again. Everything is fine. I've
met the... the intelligence that runs the place, and I've established
that it's not a threat. Quite the contrary; it's been protecting us
from asteroids for forty million years, deflecting them away from us,
not toward us.

I'm going back inside to learn more about it, but first I want to--"

"Calling Envoy. Come in Envoy. Priya, can you hear me?" Mark sounded
frantic.

"--to upload the video I've taken so far. Hold on." She set her phone
and suit cameras to upload to the capsule, where the video would be
automatically relayed to Earth.

"I'm likely to be inside for a while longer this next time around.
The alien says it'll answer my questions, so I'm going to ask it
everything I can think of. So don't worry if you don't hear from me
for a few hours. I've got plenty of air in my suit, and Spok--that's
what it calls itself--can pressurize the dome for me. I--"

"Priya! Thank God you're okay. When your signal cut out like that we
feared the worst."

"It's far from the worst." Priya looked up at the stars, and over at
Didymos just half a mile away. It was a rocky wall covering almost a
third of the sky. If Spok and its robots could turn Dimorphos
regolith into building materials, she was pretty sure humanity could
do the same with Didymos. And there was a lot of Didymos there to
turn into habitat, and spacecraft, and power satellites, and who knew
what all.

She looked back to the dome. Inside was a being whose sole purpose
was to look after humanity's best interests, and it wasn't some
mystical fantasy that she had to take on faith. Rather it was a real
being, with real capabilities and real knowledge that it was willing
to share. Maybe its original manifestation, as Santa Claus, had been
more appropriate than she'd realized.

"Oh yeah," she said, smiling, "It's about as good as we could ask for."

* * *

Jerry Oltion would like to thank Trevor and Emily and the rest of the
Analog crew for expediting this story so it would see print before
the DART mission whacked the asteroid in real life. The target date
is September 26th, 2022, which will probably make this the
fastest-obsoleted story in the history of science fiction. Or perhaps
the most prophetic?

(HTM) From: http://www.analogsf.com/wp-content/uploads/2023/02/ShepherdMoons_Oltion_ART.pdf

(TXT) detail: gopher://gopherpedia.com/0/Jerry_Oltion

tags: sci-fi

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(DIR) sci-fi