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welcome everyone um today to a tour of

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our neighborhood the neighborhood in

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space and before i begin i'd like to

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remind everyone that it's important to

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recognize why space matters and why

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exploring near us on planet earth is

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really significant this is where we will

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go as people and since we live in space

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what's happened to our neighboring

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planets is actually extremely germane to

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how we understand ourselves in fact one

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of the themes i will have

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today is things we've learned about

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earth by looking at our nearest

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neighboring planets that starts with

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mercury and venus continues through our

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own moon and goes on to mars so i'm

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going to be talking about that part of

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the solar system and again right now is

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a really pivotal time for understanding

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this this region of the solar system

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because this is where some of you may

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get to go

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so it would be really pretty cool it's

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been a generation since any human being

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has gone back to deep space so we're

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going to talk about

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mercury the moon

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venus

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the earth and mars these are the worlds

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that formed in the same neck of the

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woods as our planet now a lot of people

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forget that the planets were all born in

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a rather tumultuous event about 4.7

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billion years ago a lot of energy

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condensing matter probably a lot of dark

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energy and dark matter that we don't

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understand yet and it led to these

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planets and one of the important things

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to remember is while we look for other

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earths

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and here's our earth we have to remember

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that our earth may not always look this

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way

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so the hallmarks of our planet the water

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planet the life planet why is it named

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earth people always ask in fact water is

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inextricably linked to everything we do

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but if you stripped off the water of our

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planet our planet would look remarkably

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in some ways like the planet of venus

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and so one of the things we do as we

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study the inner solar system is we do

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comparative planetology so here's the

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earth i've unloaded the oceans you can

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still see the islands in australia

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the 90 each ridge and many other

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features and realized that our solar

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system

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is really a very interesting place

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because of how the planets have

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developed our planet developed into the

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water planet now this little slide shows

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something rather embarrassing about how

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we see ourselves here's the earth and we

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have a time series for the planet earth

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based on the history of life

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we're a living planet so we have

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eocambrian or

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uh pre-phanerozoic and all these eras

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defined by fossils and things like that

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very important we've developed similar

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things based on other indicators for the

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moon and now mars and mercury and we

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have none for venus

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so our neighboring world venus 90 of the

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size of our own planet we haven't

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developed that kind of paradigm this is

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a real kind of embarrassing thing it'd

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be like having a sister and not knowing

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what she really looks like

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um i don't know whether that matters to

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you but to me as a planetary scientist i

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worry about not understanding this

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planet so we're going to come back to

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venus but we're going to start with the

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innermost solar system briefly because

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we're learning about it very

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dramatically move to venus the moon back

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to earth and on to mars and i hope

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you'll

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at least be inspired by what we've

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learned in the last couple decades

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because that's the lifespan of which a

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lot of the new data has has really borne

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fruit so right now as we speak a mission

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known as the messenger mission is

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inbound to the planet mercury

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and this mission is one of the most

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challenging in the history of women and

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men because it's trying to get to

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mercury the cheapest safest way and

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actually orbit a planet where the

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temperature cycles are the most extreme

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we can ever imagine on a spacecraft in

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fact much of the spacecraft is a giant

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sun shield to keep the temperatures of

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the electronics so it can do its work no

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spacecraft built by women or men has

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ever orbited mercury

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we've done two flyby missions back in

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the 70s and now this mission has flown

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by mercury twice

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changing our view of this world that

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looks remarkably like the moon the

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problem is that's not the way mercury

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works

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but this mission won't arrive to mercury

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to do its mapping until march 2011. so

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we're getting ready to unfold the real

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mysteries of a planet it's about a third

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the size of the earth's where we really

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don't know why its surface

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looks so much like the moon there are

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theories why it has a magnetic field the

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way it does whether at the poles of

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mercury there are actually ice sheets

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preserved inside craters so the

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messenger mission built by the applied

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physics lab competed by nasa is our new

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mission to that planet and starting in

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march 2011 we will be peeling back the

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veil of how the innermost planet and our

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solar system work this is the densest

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planet in the solar system okay it's a

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factor of 40 denser than the earth now

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to get to mercury

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the messenger spacecraft had to fly by

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and achieve a little nudge from the

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planet of venus and that's what we do we

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use the energy of the planets in the

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solar system to allow us to do what we

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do this is one glimmer of the new data

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the messenger is producing this is a

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color

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visible infrared map of the cratered

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region of mercury the colors represent

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different chemistries we see areas that

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are blue coated with a different type of

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soil or regolith we see these large

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compressive features we think mercury

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puckered because of the incredible

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incredible thermal load from being so

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close to the sun we see fresh craters

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where you see color patterns of the

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things that were ejected from them so

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there's mercury i wish i could tell you

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how this planet put itself together

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because we don't know however we have a

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mission

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to go it's not a place we would likely

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send any of you

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temperature extremes would not be

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prudent as a former president once said

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so missions of exploration to the

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planets in this follow in this coming

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decade will revolutionize how we see our

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innermost planet mercury and move on to

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other worlds so this is just one little

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piece of the data about mercury that we

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will have from global

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so let me turn to the planet venus

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how many of us really think about venus

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let me stop this for a second

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here's venus in the night sky you can

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see it tonight a bright

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fourth magnitude

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feature it's the brightest thing in the

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sky other than the moon

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this is a winter shot from the last

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winter what's interesting about venus is

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a lot of astronomers are now coming to

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think as we look for other earths we

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better keep our mind's eye open to venus

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what makes venus interesting big okay

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some of us might think that rocky

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planets can only get as big as those we

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have to get too big they break apart

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they can't don't have enough internal

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strength secondly it has a huge

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atmosphere if you were standing on the

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surface of venus and i do not recommend

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that very hot if you were

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the dents of the atmosphere would be

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slightly about 10 times less dense than

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water and it's a gas

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so it's a actually a supercritical fluid

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made of carbon dioxide so imagine how

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that kind of planet works it's more like

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the gases coming out of the uncapped oil

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wells down deep in the ocean than

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anything we can imagine being here on

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planet earth

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so venus the morning star sometimes the

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night star i might add

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is really an enigma giant atmosphere

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through our eyes that's what all we see

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a fuzzball cloud decks we know those

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clouds now are partly

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comprised of of sulfuric acid droplets

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and other nasty caustic chemistry

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there have been

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more than a dozen missions by the nation

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formerly known as the soviet union to

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explore venus the united states has sent

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two missions to venus specifically one

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in the late 70s and one called magellan

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but this is the view you'd see of the

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super rotating outer atmosphere now in

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the early 90s the united states mapped

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98 of venus with a mission known as

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magellan using using something called

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synthetic aperture radar these globe

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views show the planet seen by radar at

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about the scale of or

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about the scale of the modus instrument

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on our earth observing system terra and

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here's a map

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and i'll stop this of one region of

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venus one hemisphere

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and the big features you see here are

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each the size of the united states

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they're huge this is a giant mountain

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system with rift valleys and other

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features and basically what you see here

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is color-coded topography with radar

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backscatter the problem is the scale

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you're seeing is weather satellite scale

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as planetary scientists as people we're

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used to the scale that we feel and touch

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and walk as geophysicists and others so

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the scales we have for venus aren't

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enough to tell us what made that are all

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these blue areas places that are low

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because at one point they were

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oceans wouldn't that be cool today the

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present conditions for venus would not

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support the existence of liquid water

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the average surface temperature 450

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degrees centigrade

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average surface pressure about 100 bars

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okay 10 megapascals this is not the kind

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of place you'd like to go not the place

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we're thinking about for human

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exploration however in the story of

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venus is a story that we need to be

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aware of for our own planet and this is

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very important so there's the visible

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venus big atmosphere the actual outer

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atmosphere super rotates in a period of

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two days the whole atmosphere goes

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around

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sort of like our earth's atmosphere the

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lower atmosphere of venus that you see

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here through the eyes of radar slowly

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rotates retrograde

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so in fact a year a day is longer than a

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year on venus imagine that

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why venus doesn't have natural

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satellites we don't know venus doesn't

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have an obvious giant magnetic field why

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not big hot planets tend to have those

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earth jupiter mercury what's going on we

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don't know

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what made venus climate system today

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hellishly hot caustic not friendly to

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life possibly superoxidizing what made

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it that way did was it born that way

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very unlikely it's hard for a planet to

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be born that way for many reasons so

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what made it go into a runaway situation

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again we don't know the last mission to

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venus was by the united states which