Monthly Archive for July, 2011

Dawn arrives at Vesta!

(I was going to call this post “Dawn breaks at Vesta” but that might have given the false impression that Dawn literally broke in orbit and isn’t working anymore 😉 )

Dawn successfully entered Vesta orbit in the weekend, and has returned the first pictures from Vesta orbit!

Vesta! (Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

The big lump in the middle of the asteroid is actually the central peak of a massive crater caused by an impact that literally blew away most of the protoplanet’s southern hemisphere! There are all sorts of interesting things to see here – lots of bowl-shaped craters, grooved/scallopped terrain in the big crater floor, and what looks like a huge cliff marking part of the rim of the big crater!

There’s also a very nice image showing another view of Vesta’s ‘south pole crater’, along with other asteroids that we’ve sent spacecraft to shown to the same scale:

Vesta, with other asteroids (Image credit: NASA/JPL-Caltech/JAXA/ESA)

Vesta is about 530 km in diameter, so it’s pretty large for an asteroid – it’s the third largest in the asteroid belt – and is far bigger than Lutetia, which was previously the record holder for ‘largest asteroid visited by a spacecraft’. Dawn will move on to visit Ceres next year, which is the largest asteroid in the asteroid belt and (unlike Vesta) is actually spherical too.

We’ll see more of Vesta as Dawn maps it from orbit over the next year – this only the beginning, and I’m very excited to see what else will be revealed! (You can find out more about the Dawn mission at its official website)

Approaching Vesta!

Vesta! Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

On July 15th, NASA’s Dawn spacecraft will be entering orbit around the asteroid Vesta – and I’m really looking forward to it! This is a new frontier – while we’ve seen a few small asteroids (e.g. Ida, Gaspra), we’ve never seen a big asteroid up close, and Vesta is the third largest asteroid in the asteroid belt between Mars and Jupiter (it’s also the second most-massive after Ceres, which will be visited later by Dawn). We’ve also found several meteorites on Earth that we think were blasted off from Vesta’s surface by impacts on the asteroid – these indicate that Vesta should have differentiated into a rocky mantle and metallic core, and I’m curious to see if there is evidence of volcanic activity on its surface (my Ph.D. supervisor published some papers about Vesta’s early history, and some of his interest and enthusiasm about it has rubbed off on me!).

Asteroids are interesting beasts – they’re mostly found in the space between Mars and Jupiter, and are remnants from the formation of the solar system. The rocky planets in the solar system formed by accretion in the solar nebula about 4.6 billion years ago – put very simply, dust grains clumped together due to gravity to form planetesimals, which themselves clumped together to form protoplanets, which then clumped together to form larger planets. However, Jupiter’s gravity affected (and still affects) the orbits of nearby objects, which prevented the asteroids from accreting into planets. As a result of this, we now have a band of asteroids between Mars and Jupiter – it’s essentially debris that was never allowed to form into a planet. What’s more, if you could combine all the asteroids currently in the asteroid belt, the resulting object would be smaller than our own moon (part of this is due to the fact that many asteroids have been ejected from the belt by gravitational interactions or destroyed by collisions)! Since we’ve not seen a large one up close before, a lot of planetary scientists will be interested to see what Dawn reveals at Vesta (and later when it moves on to orbit Ceres, which is the largest asteroid and also a dwarf planet).

As Dawn has been approaching Vesta over the past few weeks, features have been slowly coming into view that we couldn’t see from Earth. The latest picture (shown above) hints at interesting features – for one thing, there don’t appear to be an awful lot of large craters visible, which would imply that its surface may be young (possibly evidence for volcanic resurfacing?). Some curvilinear features are also visible in the southern hemisphere – maybe they’re tectonic in origin, or perhaps they’re something else (crater-chains? flow fronts?). Right now it’s all very tantalising, but we’ll find out more when Dawn goes into orbit in a few days!

[Book Review] The Demon-Haunted World, by Carl Sagan

Demon-Haunted_WorldSummary: If everyone read and understood this book, the world would be a much more sensible place. It should be required reading for everyone, whether they’re interested in science or not.

Review: The Demon-Haunted World: Science as a candle in the dark is in my opinon one of the Carl Sagan’s most important works. In it, Dr Sagan does nothing less than explain how science works, and provides a clear framework for readers to understand how to view the world rationally and skeptically.

While the internet is potentially a veritable goldmine of information, nowadays it is a double-edged sword. On the one hand, it’s a great resource for research and learning about the world if you know how to look for relevant material and how to assess it and filter out what you don’t want or need. On the other hand, there’s a lot of noise to wade through, consisting of wacko pseudo-science, crazy conspiracies and New Age ideas like the end of the world in 2012, Nibiru, faked moon landings, “Intelligent Design”, religious raptures, magic healing rocks, crop circles, “energy healing” and other such nonsense. Much of this is presented “authoratively” and if a reader doesn’t know better – or doesn’t know how to question these ideas – then it’s not surprising that people can be taken in by them.

While many of these ideas gained popularity after the book was first published in 1996, The Demon-Haunted World is aimed at addressing this problem. Thematically, the book is divided into three parts – the first few chapters present some of the pseudoscience ideas (those prevalent during the 1990s, at least) and debunks them by discussing them skeptically and presenting reasoned scientific arguments against them. The second part – the meat of the book – presents the “Baloney Detection Kit”, which describes how science works and how to think logically and skeptically about what you’re presented with in order to determine an idea’s validity. Can the idea be tested? Can the facts be confirmed independently? What happens if the idea is extrapolated beyond its initial statement, etc? This is an invaluable manual for honing one’s critical thinking skills – something that sadly doesn’t seem to be taught much as a specific subject at schools and universities, and seems to be very much lacking in the world today. The final part of the book is more a collection of essays related to the theme of science communication, the standard of science education in the US, and freedom of expression (with a bit of politics thrown in) – not directly relevant to the rest of the book perhaps, but still an interesting read.

Science is presented as a “light” that shines against this oncoming “darkness” – dramatically put perhaps, but I do genuinely think that there is a real danger that scientific ideas are slowly being cast aside in favour of superstitious nonsense. Already we have had politicians with “faith-based policies”, “alternative medicine” touted as being superior to real medicine without clinical trials or peer-reviewed studies, and pseudoscientific garbage against evolution presented as a valid alternative in school science classes. Is this really where we want to be in the 21st Century? I don’t think so, and I fully believe that these ideas should be actively fought against wherever they may arise.

The Demon-Haunted World most likely won’t convince people who are already hardcore believers in pseudoscience of the fallacy of their ideas – they’re probably too far gone for that – but it can at least be used to immunise others against their ideas. It provides a very useful mental toolkit, not only when it comes to understanding science but also for constructing a rational view of the world in general. As such, I think everyone needs to read this book!