No-one knew just who was going to organize the human exploration of the cavern. In the end, DEEP ended up overseeing it, and the budget and expertise was pooled from all the organizations involved (plus a substantial grant from the National Science Foundation).

Dan Robbins, of NASA's Jet Propulsion Laboratory, was voted the chairman, and final responsibility rested with him. After two months of analyzing the scientific findings from the probes, the group met again at JPL in Pasadena.

The atmosphere was electric. Everyone knew why they were here this time: humans were going to go into the deep, dark places of the earth. Way deeper than ever before. President John F. Kennedy's famous 1961 speech setting the vision for manned exploration of the moon was on Dan's mind, and he mentally paid homage to it as he called the meeting to order. He tipped up the brim of his hat.

"Esteemed colleagues, we have a new challenge before us today. An opportunity has opened up, quite literally, and men and women will venture deep into the earth. We have no blueprint for this. There is no vehicle existing today that can take us there. We will face pressures equivalent to the deep ocean, and temperatures equivalent to a broiler, in an oxygen-less environment. We have to get in there and back out through a tiny hole in the earth's crust. We will face unknown dangers. If anything malfunctions, the explorers will be beyond rescue.

Gentlemen, we know more about the surface of the moon than we do about this place. The first thing we have to focus on is the vehicle that will take us there. Besides, there isn't even a word in our vocabulary for this type of explorer. I am open to all suggestions on this matter.".

Silence. A nervous cough.

"Terranauts" someone said at last. Nods and murmurs of agreement all around.

"Okay, so that's settled", continued Dan. "Now, since we will be facing dozens of atmospheres of external pressure, instead of one atmosphere of internal pressure, I'm not sure who to call first: a submarine builder or an aerospace company."

Laughter all around.

Both marine and spacecraft engineers were present in the meeting, and a discussion of the design problems began.

Valery Vikentyev of the Moscow Institute of Physics and Technology spoke up first. "Our problems are twofold." he began in perfect, but heavily accented English. "We have to have a pressure hull that can withstand deep sea pressures, but we can't use air-breathing engines of any kind. That only leaves us with rockets. We are not sure if it is even technically possible to lift this kind of weight, with the burn time that will be required to take us to the bottom of this cavern and back."

Most everyone with any kind of technical background had been mulling these problems for months now, but there it was on the table. This was their moon mission. A crew of four were required: two pilots, and two geologists.

Gradually, technical details and suggestions were hashed out. Designs were proposed, then thrown out. The huge smartboard at the front of the room was used and re-used, as each member scribbled on his or her own tablet for all to see. Sketches popped into 3D renderings. Calculations were run in real time of material strength, engine thrust, mass, fuel burn rates, life support requirements (including an extremely powerful air conditioning unit to cambat the heat), and numerous other variables. An evolutionary process was taking place. Ideas with merit were refined, and others that were unworkable tossed out. It was technology-enhanced brainstorming.

Eight hours later, much had been accomplished, but an impasse had been reached. The leading design was an egg-shaped pressure hull, made from three-quarter inch thick titanium, about ten feet long. This would give a cramped but workable space for the crew, their life support equipment, the science instruments, and the cockpit. The windows consisted of four round portholes, each two feet wide and two inches thick. The fuel tanks and rocket engines would be outboard, on a strong but light triangulated truss. This would also house the radars, lights, cameras, spectrometers, gas chromatographs, LIDAR, and a sample collection arm.

The problem was, all together it would weigh on the order of 24 tons, without fuel. It was no lightweight lunar lander. It was operating in more than six times the Moon's gravity and against the resistance of thick, soupy gas to boot. NASA had had it easy.

There were two main mission targets: the cavern floor, and the opening at the side discovered two months earlier. It was clear it couldn't carry enough fuel to reach the cavern floor and return. Reluctantly, it was decided that a manned mission to the floor was not feasible. That would have to be left to robotic probes - maybe a rover to find samples, and a later sample return mission to bring them back. That left the opening.

"We're still pushing the design limits to even reach the opening, because we have to fly so far across the cavern, instead of just going down" said Dan. "We could maybe shave a few millimeters off the wall thickness, because the pressures won't be as great as they are at the bottom, but I don't know if this is even gonna work."

The disappointment in the room was palpable.

"How to reduce the fuel weight?" asked Serena McNaughton, of the National Oceanic and Atmospheric Administration.

"Parachutes" came the reply, from across the room. "We won't use rockets at all on the way down. We'll use a steerable parachute system till we get close to the hole, then jettison it and use rockets the rest of the way in and to get back up."

"Brilliant" said the engineers, almost as one. Quick calculations showed it could be done. They had their underground spaceship. Now, they just had to build it.