Translator: Tijana Mihajlović
Reviewer: Denise RQ Good afternoon. I'm going to talk today
about the wonders of our Solar System and I'll put this in perspective: humans have looked back
over their accomplishments over many, many years and centuries and they have selected
enormous achievements that they have done. We all know about
the Seven Ancient Wonders of the World: the Hanging Gardens of Babylon, the Lighthouse in Alexandria, the Pyramids of Giza, etc., etc. But today I'm going to talk
about the 7 wonders of the Solar System. Some of these will be familiar
- at least you'll think they're familiar - but I'm going to talk
about new discoveries that have occurred
only in the last several years. Because of that,
they have become new worlds, new worlds of interest to us. And, oh, by the way, if you think the comet encounter
that we had this morning will be one of the seven,
well, you'll just have to wait. For the first one,
I want to talk about this planet. This is the planet Mercury. It's our smallest terrestrial planet. It is the closest one to the Sun,
and it is an unbelievable object. We have flown by this before,
in the 60s, in the early 70s. Very cratered. The images looked horrible. But we've done this more recently
with the spacecraft called Messenger. These are two images
from 2 of the 3 flybys that it has done, and it's looking at Mercury
with brand new sets of instruments, and these instruments
are looking in the infrared. As Mercury heats up from the Sun's light
and emits in the infrared, we're able to detect major changes. Those changes tell us
about the mineralogy on the surface. The mineralogy
is all about how it is composed, and how material has been brought to it,
or it is gathered, or it has accreted in its position
in its early part of the Solar System. As you can see,
the colors are spectacular. In the image on the left,
in the upper part of it, a huge region called Pleora's Basin. We now know, based on the mineralogy,
that this is of volcanic origin. Some of the craters that have hit -
that have been created from impacts of a variety of materials
that has hit this planet, has generated array structures
that reach halfway around the planet. But a couple of things that are
just absolutely striking about this: this planet is bigger than our Moon,
smaller than Mars, we would assume it would have
a density in between the two, but Mercury is almost
as dense as the Earth. What happened to it? Did it accumulate a huge amount of iron? Was it crushed? What were the conditions
that made Mercury what it is today? It has a core. The core is bigger
than the core of the Earth. It generates its own magnetic field. It pushes the solar wind aside,
except for two places in the pole, for which solar wind material impacts
right at the top of the pole, sputters material off, sodium comes up of the magnetic field and goes down the tale,
along with magnesium. If we look at Mercury
in just the right way, we see these long tails
of sodium and magnesium going outstreaming into the solar wind. Things that we've never seen before;
Mercury is truly a new world to us now. And what matters next for Mercury,
Messenger, once again, is coming around and in March 2011, it will ease
into orbit around Mercury for two years and make spectacular measurements and help solve the mysteries
of why Mercury is the way it is, and perhaps why other planets
around other stars will look like Mercury. The second one I want to talk about. This is the Earth's Moon
like you've never seen it before. Now, it is the back side of the Moon and, of course, we have
to have a spacecraft to see it if we are going to look at the back side. But we have colored the Moon
from red to blue in the spectrum. The red indicates
- and the white part of the red - the very highest parts
of the back side of the Moon; the blue indicates the very lowest parts. The difference is about 19 km,
and that is an enormous distance. In fact, there is a 19 kilometer distance
here on the Earth if we go to the Marianas Trench,
11 kilometers deep in the ocean, and then go to the top of Mount Everest;
that is the difference of 19 kilometers. The region in blue
that's in the southern hemisphere is a huge region - this basin we call it - stretches from the south pole,
all the way to a crater called Aitken. We call the basin South Pole-Aitken basin. The Moon really took one for the Earth. Some enormous collision
happened in its past that carved this region out,
blew away most of its crust. The lower mantle is right there,
the lower crust is right there, perhaps the mantle was there. We cannot even get
to mantle material on the Earth, and yet, it may be on the back side
of the Moon for us to look at, and understand how planets like these, our terrestrial planets and moons
are put together. The Moon is truly a beautiful object
and one of further study. The next one that I want
to talk about is Mars. We've talked a little bit
about Mars today. Mars is most Earth-like. If humans were ever
to leave low-Earth orbit, Mars as a destiny would be a worthy place. But when we first flew by it,
and we looked at it, it also looked very cratered. We thought it was more like the Moon,
and it took us a while to realize that Mars was much more fascinating
than just cratered object, Moon-like. So, we put in place a program
over the last 10 years to look at Mars in a rather unique way,
and that was trying to find the water. We see from a distance
the white polar caps - that's carbon dioxide snow,
that's not H2O - but is there H2O there? Did H2O, water, exist on Mars in the past? Was it wet in the past
and could it have harbored life? If it was wet, the probability
that it harbored life is great, and we would like to know that. But what we found
over the last several years when we looked at Mars
in many different ways is signs of past water
everywhere we've looked. We've landed a system called Phoenix
in the northern polar region. It dug down, it found a water layer, and it tasted it,
and it was 99.9% pure water. The rovers, Spirit and Opportunity, fine laying on the ground,
these little round nodules, that are seen in this. We call them blueberries; it's sort of what they look like,
describes their size. They are hematite. They're iron oxide that's made
in the presence of minerals and water. We have seen what looked like deltas, fast moving water that has taken material
and dumped it down, much like our deltas here
in the end of the Mississippi. And most recently,
from Mars Reconnaissance Orbiter, we see fresh craters being created. Fresh craters being created. Yes, Mars is bombarded
just like the Earth gets bombarded, just like the Moon gets bombarded. It happens all the time. And these fresh craters,
as we fly over them, we see white material
laying out along the edges. In about 40, 50, 60 days
as we pass over again, the white material is gone, so we've taken spectra,
and the spectra is spectra of water. We've uncovered water layers
mid-latitudes on Mars, and we believe they are extensive. Our ground penetrating radars
since indicated that there may be several stories thick and what we're looking at
is perhaps a buried glacier. When Bobby Braun talked today about bringing material from Earth
to sustain life, I'm sure he was thinking
about vast amounts of water, and I'll tell Bobby next time, "Leave the water at home,
bring your straw." (Laughter) But Mars is not done surprising us. We have looked
over the last several years at Mars, and we see methane coming out. The methane is shown on the right side,
sorry, your left side. The red is intense methane plumes and we find,
after looking over many years, that they're variable,
and they vary with season. Methane can be produced
biotically or abiotically. And what matters next is a mission
we call Mars Science Laboratory which we will launch
in November of next year. It's the size of a small car. We will put it down and it will measure
the isotopes of methane, and it will help us determine,
at least one step closer, whether Mars is actually
harboring life now or not. I want to go to the next wonder, Europa. This is a moon of Jupiter.
It's a beautiful moon. When you look at this, you realize that this moon of Jupiter
is about the size of our own Moon, the first thing you say is,
"Where are the craters?" I only see one, maybe two. Europa has resurfaced itself. The gravitational interaction
between the planet Jupiter and this moon, and this moon and the other moons,
the other Galilean moons, produces heat in the interior,
and it melts the water in this moon. And we now know that underneath the ice crust
that's shown here is an ocean, and that this ocean contains more water
underneath the crust of Europa than we have water
on the surface of this Earth. And this sits
in the radiation belts of Jupiter and those radiation belts
really hammered it. But in our models, we now realize, that as it associates H2O
and the ice, the hydrogen leaves, but the oxygen diffuses through the crust
and maybe oxygenating the ocean, the astrobiological potential
of this moon alone just jumped in order of magnitude. Truly a wonder of the world, and we're planning a mission
to 2020 to go to Europa. The next one is Enceladus. This is a fabulously wonderful
ice-ball moon, very small - it's only about
few hundred km in size - just outside the rings of Saturn. It has also tidal interactions
from the huge planet Saturn and those tidal interactions are heating,
melting the water underneath the surface, and it is coming out in its cracks,
in huge geysers. And we have flown
through this with Cassini, and Cassini continues
to monitor these geysers and indeed, we also find
that this moon has about 99.9% water coming out of these cracks
in these huge geysers. These geysers go out throughout the system
and actually form what we call the E Ring. You can see in the lower right that's actually part of the ring
that goes around Saturn. It is the E Ring. What matters next
as we continue keep Cassini moving, making observations in this environment so that we can understand this moon
and its effect on the system better. Number six: this moon
is also a moon of Saturn. It is called Titan,
and it is a fabulous moon. It has a rather thick atmosphere, much like ours
in the sense of its pressure. It's about what we call
one bar down at the surface, but it is far more fascinating
than many other objects that we've studied because it is the only object
in the Solar System that we have found
that has liquid on its surface. It's not like liquid water;
it's liquid methane and ethane. We find well over 200 lakes already, and we've only just scratched the surface
of looking at Titan with our radar. Titan is even more important than that. This object is huge. It's bigger than Mercury. If we were to pull it away
from gravitational interaction with Saturn and put it in its own orbit
around the Sun, we would call it a planet. And this planet is much like early Earth with its chemistry
and its hydrological cycles. It's raining methane right now as we speak
in the southern hemisphere of Titan. It is an early Earth. It is a birth Earth, and we need to know more
about this fabulous moon. Cassini will do that for us. It will last for another several years
and continue on. And now, let's talk about
the seventh wonder that I chose today, and we'll start by talking about
the comets that I mentioned earlier. These are the four comets
that we have imaged with our spacecraft: Halley, Tempel, Borrelly, and Wild 2, and as you can see their sizes,
and these are their relative sizes, as they get smaller,
they may be more spherical. Perhaps we expected
Hartley 2 to be spherical. And as you can see,
even though these comets are active, the plumes are hard to see, because the comets themselves
were so close; we were only imaging the surface. So, here is the data from Hartley. This is one of the first images
that was sent down. Not all the data is here yet,
but this tells us the spacecraft survived. It turned its antenna towards us,
30 minutes after it made the encounter, and then took the last two hours
getting the data back. This comet is unbelievable. It doesn't look like
any of the others in many ways. It has these smooth features
between these two nodules. Some of these nodules are very rough. It is incredibly active. We see material being poured out
in every direction. And we were talking about classifying
this object with the rest, and perhaps we're missing the point. Perhaps what we're really looking at
is an evolution of how these comets live and die
as they go around the Sun. Now, what matters next
is that we have another comet encounter. We're going to go back to Tempel 1. We're going to fly by Tempel 1 in February
- February 14th as a matter of fact - and we're going to look at it
with a spacecraft called Stardust and the importance behind that is that comet has already gone
around the Sun, it's already gone through
its maximum sublimation phase, and we will look at it
after that has occurred. So, we will see the before and after
of that evolutionary stage, a blasting material
sublimating that material and pouring it out into the Solar System. That will truly be exciting,
and that's what matters next. And I want to end
with this particular picture. It turns out to be one of my favorites. It's actually Cassini
measuring Saturn in the dark, and it took 12 hours to make this. The Sun is on the other side
of the planet. What's really exciting about this is that light we receive
is reflected off the rings, reflected off the planet,
reflected off the rings, and comes back to us; a very dim light, and we've seen it. But the discovery here is right there. If you can see the dot, that is Earth, and we're beaming the data
that you're seeing back through the rings to Earth, the small, blue, beautiful, beautiful Earth. That's what matters next. Thank you very much. (Applause)
