Robot Recon: Our First Steps into the Solar System

Sunday 21^st July, 3.30pm

The Illuminations theatre and planetarium on Queen Mary 2 is quite possibly the largest, and certainly the grandest, room I’ve ever had the privilege of speaking in!  Occupying both Decks 2 and 3 forward, this will be the venue for all of the Cunard enrichment lectures over the coming days.  As preparation for my lecture, here’s a loose transcript of the things I intend to talk about. 

Note that many of the images used throughout this lecture series can be found here:  http://pinterest.com/leighfletcher/planetary-imaging/

I start the lecture with a recent Cassini spacecraft image of the tiny moon Enceladus, showing a brightly-lit crescent, its dark side illuminated by light reflected from Saturn, and signs of the south polar geysers spewing icy material into space.   After nearly a decade on its lonely orbit around Saturn, almost a billion miles from home, the Cassini spacecraft has revealed breath-taking new views of the ringed planet that simply would not have been possible without the intrepid robotic explorer.  The solar system is full of wonders that remain to be discovered, and our reconnaissance of these worlds is only just beginning.  The past two decades has seen an explosion in the number of planets discovered around other stars (900 and counting), and yet we can know very little about these distant worlds – they are simply too remote for us to ‘see’ their surfaces, oceans and atmospheres.  Our own collection of diverse planetary environments therefore serves as a template for what makes a planet, and as the only examples humankind can hope to explore in the near future.

The Planetary Fleet in 2013

The planetary fleet in 2013 comprises a range of unique, sophisticated spacecraft exploring our solar system.  These range from orbiters around the inner planets Mercury, Venus and Mars; rovers on the surface of Mars; probes en route to comets and asteroids; Cassini in orbit around Saturn and Juno en route to Jupiter.  Even the dwarf planet Pluto is destined to have its first visitor, the New Horizons spacecraft, in the next three years. Only the ice giants Uranus and Neptune remain unexplored since the 1980s.  These spacecraft have given us glimpses of both the unfamiliar (such as our entire planet viewed in a single pixel from the Voyager spacecraft in 1990); to the strangely familiar.   Indeed, I show a comparison of surface images from Venus, Mars, Saturn’s moon Titan and the surface of an asteroid, trying to show that processes familiar to us on Earth (flowing liquids and rivers, erosion, mountain ranges, craters) are common to all of these worlds.  Indeed, our experience of the diverse environments of Earth is precisely the toolkit planetary scientists need for an understanding of the planets.

Today five missions are active at Mars, including Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter in orbit around the red planet; and the Opportunity and Curiosity rovers on the surface.  I show the audacious landing of the Curiosity rover in August 2012, a feat of extreme engineering, and what the future holds for this car-sized, nuclear-powered rover in Gale Crater.  I also show an image of a Martian sunset, obtained by the Spirit rover before its demise. For Mercury and Venus, I show the powerful solar activity that these inner worlds (and their robotic visitors!) must contend with, including the latest results from the Messenger spacecraft at Mercury and Venus Express at our ‘evil twin sister’ planet.  Venus’ thick carbon dioxide atmosphere serves as a blanket, retaining the sun’s warmth and making the planet the hottest place in our Solar System, an example of a runaway greenhouse effect, the nightmarish end product of adding too much CO2 to an atmosphere, as we are currently doing on Earth, and a stark warning on the dangers of uncontrollable climate change.

The Realm of the Giants

The Outer Solar System is the realm of the gas giants, and an extreme challenge to exploration due to the longevity of any mission heading for the distant outer reaches.  I describe the trajectory of the Voyager spacecraft as they visited Jupiter, Saturn, Uranus and Neptune, and are now the most distant human-made objects at 124 and 102 AU (an astronomical unit is the distance from the Sun to the Earth) from the Sun for Voyager 1 and 2, respectively.   Starting with Jupiter, the banded appearance is the natural meteorological state for a spinning ball of fluid uninterrupted by continents, mountain ranges, valleys and oceans, and there’s even evidence for banding within our own atmosphere and ocean on Earth.  Superimposed onto these bands are enormous storm systems like the Great Red Spot.  Jupiter is accompanied in its 10-year orbit around the Sun by a diverse collection of satellites, the worlds of fire and ice that would each be a fascinating destination for future exploration in their own right, from volcanic Io, to Europa with it’s icy crust and sub-surface ocean, to the giant moon Ganymede (larger than the planet Mercury) and ancient, battered Callisto.  Europe will ultimately launch an ambitious new mission called the Jupiter Icy Moons Explorer (JUICE) to visit these worlds in the early 2030s.  I won’t dwell on Cassini’s exploration of Saturn in this talk – for that you’ll have to come to my lecture on Friday!

On to the realm of the Ice Giants, Uranus and Neptune, and I show how strange these two worlds are – Uranus, having been bowled over onto its side during some cataclysmic event in its distant past now suffers the strangest seasons of any planet in our solar system.  Neptune, despite being the most distant planet from the Sun, receiving 1/900^th of the solar energy input as Earth, nevertheless has some of the most powerful meteorological events of any planet due to its reserves of internal energy.   I show the parting shots of the ice giants taken by Voyager 2 in 1986 and 1989, and ask whether we will return to these worlds within the next half century?

Finally, we wait with anticipation for the New Horizons flyby of Pluto in 2015.  Although now visiting a world demoted from planet-hood to the status of ‘Dwarf Planet’ in 2006, recognising its membership of the group of similar objects known as the Kuiper Belt beyond Neptune, this mission will reveal vistas that no human has ever seen before.  Even the best views from the Hubble Space Telescope are blurred and indistinct, and we are privileged to live in a time when a truly unknown environment will be revealed to us for the first time. 

I finish the lecture with an image that I believe encapsulates the essence of robotic reconnaissance of the solar system – an image taken from the shadow of Saturn.  No human can ever see this view, only our robotic explorers can reveal it for us.  And yet, for all the wonders that these robots have revealed, their most important contribution to human society has been to show us our place in the universe.  In this Cassini image of Saturn, we see a distant view of Earth obtained from a billion miles away.  Every human, alive or dead, is in those few pixels.  All of our history, everyone we’ve ever known and loved, sharing those pixels as imaged by a nuclear powered explorer in orbit around a distant ringed world.  Exploring our solar system places our own fragile, beautiful world in its broader context.