Before we get started, we wanted to let you know there’s some new
limited edition Merch for sale at the Merch store.
North America was recently graced with a total solar eclipse.Those of us lucky or
obsessed enough to be on the narrow path of totality and … also lucky enough to
not be under a giant blanket of clouds … witnessed this most wondrous of all
celestial phenomena. The Sun went dark, the solar corona blazed, and even the ruby-red
top of the solar atmosphere became visible to the naked eye. Jupiter, Saturn, Venus,
and even a comet straddled the new black-hole Sun. Part of the reason the total solar eclipse
is special is that it’s so rare. If it happened every day you probably wouldn’t even look up.
Well, good news for those of us who missed the eclipse, whether due to weather or geography
there is such a phenomenon. It’s that enormous ball of rock that’s just hanging in our sky. The
one that happens to be the exact size to blot out the Sun now and then, and without which we
may never have figured out how the universe works—or begun our exploration of it. It’s
the Moon, and it’s our stepping-stone to the universe. Today we learn how to take that step.
INTRO MUSIC
Seriously, our Moon is crazy. You know those over the top science fiction sky-scapes—multiple suns,
multiple moons, gigantic moons or Saturn-like planets or crazy nebulae that fill half the
sky. The reason we have to come up with that stuff is because our own sky is already pretty
sci-fi over-the-top. No other planet in our solar system has anything like the Moon. The
only physically larger natural satellite are 3 of Jupiter’s and one of Saturn’s moons,
and our Moon is still comparable to those in raw size. But the gas-giant moons are tiny
compared to their host planet. Our Moon is by a long, long way the largest relative to
the planet it orbits, making the Earth and Moon practically a binary planet system.
It’s generally believed that our moon formed when a Mars-ish-sized planet that we call Theia slammed
into the still-forming Earth, throwing up one of those sci-fi planetary rings that quickly pulled
itself together into the Moon. And we’ve talked about this hypothesis before. That seems like
a rare enough event that some argue that such outsized moons are probably rare in the cosmos.
If so, then an alien looking up at our sky would be like what the hell is that
thing? And then they might think that it’s no wonder these otherwise primitive humans were so
quick to figure out so much about the universe from the big bang to the end of time. I mean,
we could only pretend that we are at the center of a small universe for so
long when we can literally see the detailed surface of another world with the naked eye.
The Moon is both our metaphorical and literal stepping stone to the universe. I’ll come back
to the literal part in a minute—let me just drive in the metaphorical part a bit
harder. The Moon gives us a few telling clues about our place in the universe.
1) It's round. The moon is pretty clearly a giant ball of rock with a cratered surface.
It’s a world. Surely an essential clue that the other bodies of the solar system,
including the Earth, are of similar form.
2) Its eclipses and lunar phases. We saw this last episode. These phenomena told us the basic
structure of the Earth-Moon-Sun system, but also allowed us to figure out the distances
to the Sun and Moon—our first hard calibration of the immensity of space. And watching the
Earth’s round shadow cross the Moon really drilled in the whole Earth isn’t flat thing.
3) The Moon's gravitational attraction to Earth. It’s said that Isaac Newton figured
out his law of universal gravitation after watching an apple fall. But the
other part of the story is that to figure out the relationship between gravitational
force and distance he needed a much more distant object that is also subject to
Earth’s gravity. He used the Moon. Without the Moon it may have taken much longer to figure
out gravity. And without that don’t even think about starting up a space program.
So the Moon has been one of the most important theoretical stepping stones to our understanding
of the universe. And we’ve long understood that it could also be our literal stepping stone:
It is humanity’s first destination beyond our atmosphere. Through the Apollo programs
humans walked on another world. The last time that happened was over half a century
ago. It’s no longer something we do; it’s something we did—like, back in history.
It’s been argued that we no longer need to put people on the Moon. We got all the rocks,
that particular cold war ended. And perhaps most importantly we convinced ourselves that
inter-world travel is possible. Our eyes became fixed on Mars as the next
human destination. But can you imagine us even contemplating a trip to Mars without
having first landed on the Moon? Thanks Moon—job well done. Please continue your regular duties
of sloshing our oceans and making the night a bit more romantic and moon-lit.
Except, are we really done with the Moon? In recent years our collective intentions
have swiveled back to the great sky rock. Just last month, the very first
private company achieved a soft landing on the Moon. Intuitive Machines managed
to touch down its Odyseus lander about 300km from the lunar south pole and took
spectacular images of the surface and gathered important data for future missions. The soft
landing could’ve been softer because Odysseus tipped over on touch-down,
which did shorten its life expectancy but didn’t dent its overall success. This was such a major
achievement because the lunar poles are more heavily cratered than the equator,
and experience extreme temperature fluctuations that landers have to be resilient against.
Intuitive Machines didn’t just achieve the first private softish landing;
this was the first soft landing by the United States in the 52 years since Apollo
17. But our return to the Moon has been building up momentum for some years now.
In August last year India became only the 4th nation to soft-land on the Moon. Its Vikram
lander, part of the Chandrayaan-3 mission, was also the first craft to land in the lunar south
pole region where it successfully deployed its Pragyan rover to explore the area..
But why this current obsession with the lunar south pole, if the poles are so hazardous? Well,
because of a game-changing fact that India’s first moon mission—-Chandrayaan-1—helped establish. It
found water at the south pole. Back in 2008, Chandrayaan-1 dropped its Moon Impact Probe
into the Shackleton Crater. The “hard-landing” craft detected significant water in the tenuous
south pole atmosphere its descent, confirming earlier evidence from a number of other missions.
To be clear, these detections are not quite direct, and require interpretation. There’s
strong evidence for hydrogen in the tenuous lunar atmosphere, likely from actual ice or
water or hydroxil bearing minerals in the soil, and direct detection of those minerals. We’ve
also known for a while that there was real water ice in the permanent shadows of some
lunar craters. But there’s an emerging consensus that there must be significant ice even in sunlit
lunar soil. That means there’s just way more water than we thought. It’s not even clear
how it got there. Perhaps it was brought in by comets, just like Earth’s oceans might
have been. Or perhaps protons in the solar wind slam into oxygen in lunar minerals to
produce H2O. There’s some evidence that that lunar surface water is being continuously replenished,
so the latter may well be important. Whatever the source, the presence of water turns the
moon from a pretty but dead sky rock into our stepping stone to the stars.
If you’ve spent any time in Arakis you know why water is such a game changer.
Although it’s abundant on Earth and Caladan, it’s heavy and so expensive
to pull out of a gravity well. It costs a couple of thousand US dollars to get every
litre of water to the international space station, let alone to the moon. Even with
Fremen Stim-suit level water recycling, good luck building a decent sized base,
let alone even a small biosphere. But an enormous lunar source makes all of this possible.
Which brings us back to human plans for the Moon, and to China. China has been vigorously pursuing
lunar exploration for longer than India with its uncrewed Chang’e program. Chang’e-3’s successful
2013 landing made China the 3rd nation to achieve a soft landing after the US and Russia efforts
both ended in the 70s. Chang’e-4 was the first anything to land on the far side of the Moon in
2019, and Chang’e-5 the first non-crewed lander to successfully return lunar material to Earth.
That was in 2020. The next Chang’e - number 6 - is supposed to launch next month and to return
samples from the apparently watery south pole. Number 7 will also mess around at the south pole,
but number 8 … Chang’e-8 will do a 3-D printing experiment using lunar regolith
and will carry a sealed ecosystem experiment. All in preparation for the next phase—a crewed
lunar base. China aims to land humans on the Moon by 2030 and by 2035-ish to establish a
permanent base in collaboration with Russia, but ostensibly as an international facility.
The United States may have been the first, and still the only nation to put a human on the Moon,
but has been distracted by another shiny thing in the sky. NASA’s space exploration
has really been focused on Mars—and with excellent reason. Besides being the next
obvious human destination after the Moon, we’ve known for much longer that Mars has water—both
to support a base but also perhaps to once have supported life. The impact of finding
evidence of that would be much, much bigger than even the first Moon landing, in my opinion. The
Moon could never have evolved life, but with water it could support our life in the future.
And so again the United States is finally turning its eyes back to the Moon. The
Artemis program aims to send crewed missions on the Moon—first in orbit and then to the
surface. It consists of the Space Launch System—a super-heavy lift rocket—carrying
the Orion spacecraft. Other vehicles will also serve the larger Artemis mission,
like the SpaceX Falcon heavy carrying the Dragon spacecraft. In 2022 the un-crewed Artemis 1
mission put an Orion spacecraft into lunar orbit before successfully returning it to Earth.
In 2025 Artemis 2 will do the same, but with people—four astronauts. And
then in 2026 Artemis 3 aims to put the first American boots on lunar soil since Apollo 17.
The other big goal of the Artemis program is the construction of the Lunar Gateway space station—a
crewed station that will be constructed in lunar orbit over the rest of this decade. This one is
with participation of the Canadian, Japanese, European, and Dubai space agencies. There has
been some criticism of Gateway—basically amounting to the question of why build a station in orbit
when you could build a station on the Moon. Fair point, but ultimately the US is planning
to build a surface base, and the Gateway station is supposed to support that goal,
as well as be a general staging station for a variety of solar system missions.
Speaking of, there’s something else that lunar water is good for. Apply an electric
current to H2O and the molecule splits giving you hydrogen and oxygen. This is electrolysis.
These gases very readily recombine into H2O, releasing the same energy it took to
separate them—but now explosively. Like, in a rocket. Water can be used to make rocket
fuel. The idea would be to place some giant solar arrays on the surface near the poles
and use the energy to slowly harvest hydrogen and oxygen, turning the Moon into a refueling depot.
The weight of fuel is one of the biggest limiting factors in determining spacecraft weight
and range. And dragging that fuel out of Earth’s prodigious gravitational well is the hardest part.
With a lunar fuel depot, the most fuel any mission needs to carry is the amount needed to reach the
Moon. From there it can be refueled for its onward journey to Mars, the asteroid belt mines, its
return to Earth, or perhaps to some destination beyond the solar system. And sure, I guess being
able to dock at the Lunar Gateway is better than having to land on the Moon before moving on.
If all goes according to the various plans, in as little as 10 years we’ll have our first
deep-space space station, our first crewed lunar base. Maybe a couple of them. And we’ll be working
towards the ability to refuel spacecraft from lunar orbit. There are plenty of other plans
also—like the giant radio telescope on the far side of the Moon that we talked about
previously. For the most part our return to the Moon seems like a positive thing, with lots of
international collaboration to build a shared and peace-forward infrastructure. For example,
the US just announced a move to create an internationally agreed Lunar Standard Time
to account for the fact that time ticks a tiny bit slower on the Moon compared to Earth’s surface on
account of general relativity. But there are signs of competition already arising, and the
whiff of a new space race in the air. China versus the US seems to be the main superpower standoff,
with each asserting their leadership. Russia is aligning more with China, Europe with the US,
and various nations sidling in one direction or the other. And then there’s the private
sector which will play increasingly large, if not dominant part of the game going forward.
Whatever the outcome, it’s coming, and pretty fast. Odds are that in the decade—perhaps much
quicker—somone will be back on the Moon or close to it. And probably that someone
will be human, which is a win for all of us. We’ve been snoozing a bit on the Moon, but soon
we’ll be walking on it. Again. And hopefully soon after, that weirdly giant sky rock will fulfil its
potential as a fortuitous stepping stone towards our future exploration of the rest of space time.
Hey Everybody. Before we go we wanted to let you know we have two new limited edition Merch
items up at the Merch store. First up is our first ever Black Hole Enamel pin. This is a
1.5 inch enamel pin on 2x3 inch holo foil backing card designed by the Space Time gfx
team. These pins are limited edition pre-sale and you will need to put your order in by April 29th
with the pins shipping during the second week of June. Once we’re out of stock from the pre-sale,
that’s it. Next up is our Star Wars inspired Space Time t-shirt and sweatshirt. Designed
by our very star wars nerdy director, you can now express your love and knowledge of the force. This
limited edition design will be available until May The 4th. And if you’d like your shirt to arrive
before Star Wars day, you’ll need to put your order in by April 25th. To put your order in,
just head over pbsspacetime.com/shop or click the link the description.