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April 2019: Asteroids, Aliens and All That

April 2019

In the show this time, we talk to Matt Smith about dusty star formation in nearby galaxies, Fiona Porter rounds up the latest news, and we find out what we can see in the April night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.

The News

This month in the news: the asteroids we're visiting, the one that quietly visited us, and a new method of Martian exploration.

First, some updates on exploration of near-Earth asteroids with OSIRIS-REx and Hayabusa2. These are two asteroid studying missions that each aim to investigate and return samples from a particular near-Earth object. Both of them reached their target asteroids within the last year, and have now returned some preliminary information.

Hayabusa2 is a mission run by JAXA, the Japanese space agency, and follows the success of Hayabusa, which returned with asteroid samples in 2010. It's studying asteroid Ryugu, which is a rare Cg-type asteroid. Having rendezvoused in June of last year, it's now launched two rovers to explore the surface. Initial findings suggest that the 1km-diameter Ryugu broke off from a much larger asteroid; its density is so low that rather than solid rock, it may be comprised of rubble that collected together after an impact. It also shows signs that it once carried water, but that it was somehow burned off its parent asteroid. As it's believed that asteroids are the source of Earth's water, its absence on Ryugu was unexpected, and raises interesting questions about the possible mechanisms behind its dehydration. Once we have rock samples from Ryugu, we'll know more about the timeframe since it split off from its parent, and possibly even identify that parent from currently known asteroids, but we'll have to wait for a while - Hayabusa2 is not expected to return to Earth until December 2020.

OSIRIS-REx is a NASA mission, investigating asteroid Bennu, and will be the first American mission to bring back an asteroid sample if it succeeds. Bennu shares a few characteristics with Ryugu - it falls under another uncommon class of asteroid, and it seems it might also be comprised of collected rubble, although it's smaller at a diameter of about 500m. However, it has one unusual feature: it's active asteroid, which are rare; only a few dozen are known amongst the thousands of asteroids identified. With OSIRIS-REx in orbit, we'll be able to examine this process closer than ever before, and maybe even determine what's causing it. In the meanwhile, OSIRIS-REx will be spending its time searching for a site that it can collect surface samples from in summer 2020. Researchers believe that the mission can be safely completed despite the occasional rock ejections, and we can expect to see it return to Earth in 2023.

Now, to an asteroid a little closer to home. Our listeners might remember the incredible dashcam footage of a meteor strike over the Chelyabinsk region in Russia in 2013, but NASA has recently reported that another event like this occurred just before Christmas last year, unrecognised until now.

A near-Earth asteroid, estimated to have been a few metres in diameter, exploded over the Bering Sea on 18th December 2018. It went unnoticed at the time as it entered the atmosphere over an uninhabited region, while the Chelyabinsk meteor caused damage in multiple cities in the region and was widely observed and reported on. The fireball produced by this asteroid can retrospectively be spotted in several images from the Japanese Himawari satellite, and was the second-largest fireball observed in the last thirty years.

An asteroid of this kind doesn't pose much of a threat to humanity. It's estimated that this one released about 40% of the energy of the Chelyabinsk meteor, which itself produced relatively minor damage - largely breaking glass in buildings - and few serious injuries. However, it does highlight the need to be able to track asteroids and their movements so that we can be forewarned if an impact will affect a populated area. NASA are currently working to map all near-Earth asteroids over 140m in diameter, and have had some success at predicting the arrival of asteroids a few metres across, but it's predicted that it'll take another thirty years before they reach their aim of mapping 90% of objects this size.

In the meanwhile, while nobody may have seen the fireball from the ground, they might have glimpsed it from the air. The fireball appeared in an area close to some commercial plane flightpaths, and researchers have been investigating to see if any flights reported seeing it. If anyone did spot it, it'd make a useful account of the event on top of being a very exciting flight.

On the subject of flight, here's a first: along with the Mars 2020 rover, NASA will be sending a helicopter to Mars in 2021. As far as helicopters go, it'll be a small one - weighing under 2kg and the size of a softball, according to design reports - but its blades will rotate at around 3,000 rpm, ten times faster than a terrestrial helicopter. This is necessary as the Martian atmosphere is far thinner than Earth's, and flight at the surface there will be equivalent to flying at over 30km in the air here - no small feat, given that the highest a helicopter has reached on Earth was around 12km.

This helicopter is considered a high-risk project, as despite NASA's best efforts it may not be capable of flight on Mars, but if it succeeds it'll be a high reward. Providing the ability to scout ahead for rovers, or to investigate areas that can't be reached by ground-based vehicles, would increase our capability to explore the Martian surface. For now, though, it's being sent largely as a test of the technology; if it doesn't succeed, the rest of the mission can continue as intended, and if it does, we can gain insight into what's needed to allow for future flying craft to work to their full potential.

Interview with Matt Smith

Adam interviews Dr. Matt Smith (University of Cardiff), who specialises in looking at dust - not around the house, but in nearby galaxies. Such dust emits in the infra-red, and as such telescopes such as the James Clerk Maxwell Telescope/SCUBA2 and the Herschel space telescope are required to study it. Matt discusses his role in leading an ongoing 275-hour survey of our closest galactic neighbour, Andromeda, and Cardiff's role in building and operating space telescopes.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during April 2019.

The Planets

Southern Hemisphere

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during April 2019.

Odds and Ends

We take a look back at a paper that appeared in the International Journal of Astrobiology, which applied evolutionary theory and natural selection to alien life to explore what it might look like under these pressures. We then had a go at reproducing one of these illustrations - do you think Josh managed to capture the alien likeness? Check our social media channels to see how we got on.

Show Credits

News:Fiona Porter
Interview:Matt Smith and Adam Avison
Night sky:Ian Morison and Haritina Mogosanu
Presenters:Crispin Agar, Tiaan Bezuidenhout, Michael Wright and Jake Staberg Morgan
Editors:Beth Jones, Lizzy Lee, Tom Scragg and Jake Staberg Morgan
Segment Voice:Tess Jaffe
Additional Effects:BBC Sound Effects (
Website:Jake Staberg Morgan and Stuart Lowe
Producer:Jake Staberg Morgan
Cover art:From eldritch horror to friendly alien! CREDIT: S. R. Levin et al.

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