Time Made Of Strawberries – Un Temps De Fraises

Astronomy

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Blog 1: Moon Monday: That Big Round Thing In The Sky

By Mélissa M Azombo

“Big round thing in the sky! You couldn’t keep away, could you?” – The Doctor, Doctor Who, Series 6, The Impossible Astronaut. The Doctor was of course right. The Moon even became the main target of the space race. But was it really worth it? What’s so fascinating about the moon that it’s worth investigating?

Well, first of all, of course it was and there are many, many fascinating things about the Earth’s moon, which make it worth investigating.  However, for the purpose of the limited dimension that is time for humans, I shall keep that to 4 points.

Craters: Inevitably, the most visible features of the moon are its craters. They are noticeable with the naked eye and can be seen very clearly with a telescope. Craters such as Copernicus, Tycho and Picard give great reason to want to enquire about and study the Moon further. This is because they give us an insight to the geology – or moonology – of the Moon. A cratered surface indicates an old surface, which has encountered impacts from other bodies, such as meteors. So is an non-cratered surface a brand new one? Not necessarily, as this shows evidence of resurfacing. The planetary body has had time to “heal its wounds”, if you wish, making the ex-cratered surface smoother over time.

Tides: Furthermore, it is a generally well-known fact that the Moon is responsible, in conjunction with the Sun for our tides, due to its gravitational effect. However, the Sun only has 45% the power of the Moon when it comes to tide. Although the Sun is much more massive, with a mass of 2.0X10³⁰ kg (That’s 20000000000000000000000000000 kg), in comparison to the moon with a mass of 7.3 X10²² kg, the Sun is also much further away from Earth than the Moon’s 384 000 km distance, at a distance of 149597871 km, a distance known to astronomers as 1 astronomical unit (1 au). As the Inverse-Square Law dominates (More on that on Wednesday), the fact that the Sun is further away means it has less of an impact on Earth’s tides than the Moon does.

So, how do tides occur? Firstly, it is important to distinguish between the 2 types of tides which exist. There are Neap tides and Spring tides. Neap tides occur when the Moon is at its waxing or waning phase, so the Sun, Earth & Moon are not aligned. On the other hand, Spring tides occur when the Sun, Moon and Earth are aligned, so the Moon is at its Full or New phase. In either case, tides are caused by the Moon’s gravitational pull, causing the waves to rise up and fall. As a result of the Earth rotating over 24 hours a day, 2 tides will be experienced per day, although some places do only experience 1. This means, if the Moon was far away enough, it wouldn’t cause the Earth to have any tides at all.

 

Position In The Sky: Once upon a time, the Moon was incredibly close to the Earth. Therefore, the Moon appeared much larger in the sky and tides would have been much greater. On top of that, there is one particular factor, which makes studying the Moon at this point in time incredibly significant. On 20 March 2015, some of the Northern Hemisphere witnessed a total solar eclipse – a phenomenon which would not have applied in the past. Had the Moon and the Sun been aligned, the Moon would have covered the Sun so that it would have completely blocked it (imagine a big crisp in front of a small crisp), due to their sizes and distances. Today, the Moon is at a distance that means in the event of a solar eclipse, it exactly covers the Sun, allowing corona filaments to be visible over from behind. This, I think is why we are entitled to be more inquisitive now about the Moon, than ever before!

So, there are tons of reasons we should keep studying the Moon, whether that is to attempt to find life it or to delve further into the Universe’s past. I could go on forever, but I am sure you don’t have that long. No, honestly. I’m sure. I’m afraid you’ve only got about 5 billion years. Want to know why? Find out in my next article….

Blog 2: Pluto: From Dwarf Planet To Superstar!

By Mélissa M Azombo

It’s Moon Monday again and get ready for more on moons – this time Phobos and Deimos – the beautifully intriguing moons of Mars. Phobos… No. Hold on a minute. Sorry. Scratch that. It turns out there’s an event that requires covering way more than this. It is Monday 13^th July 2015 at 21h41 and the entire scientific community impatiently awaits the first ever close-up, detailed images of Pluto from New Horizon’s Flyby mission. We have no idea how Pluto really looks. Well, we have an idea, at this point in time but we have no proper images of its surface but tomorrow, on Monday 14^th July 2015, we will. So, what exactly is the New Horizon’s Mission and what makes Pluto so special?

NASA’s New Horizons mission was launched on 19^th January 2006. Part of its goal was to give us more information, in greater detail about Pluto, so the spacecraft was to take images of Pluto, as it passed it, on its journey.

As you might have guessed, Pluto has not always been known about. Positioned at a 40 au away from the Sun, it was only discovered on 18^th February 1930, whereas closer planets like Mars and Venus have been known about for as long as one can think of due to Mars being bright enough to be seen in the sky and of course Venus can be seen in the night sky, too. It was discovered by Clyde Tombaugh during a photographic search. It is believed to be part of a double-planet system, with its “satellite” Charon, as Charon (discovered in 1978) is approximately half the size of Pluto and the bodies rotate in a synchronised manner, so that the same sides of each body are always facing each other. Its atmosphere consists mainly of nitrogen, as Triton’s does. In fact, it is likely that Pluto is similar to Triton, apart from geologically.

It has been the centre of scientific controversy since it was demoted to Dwarf Planet status in 2006. The reason is that Pluto has not cleared its orbit, so can not have full planetary status, according to the 3 criteria which define a planet. The other two criteria are that it must orbit the Sun and must be big enough for the Sun to squash it into a sphere. Unfortunately, Pluto falls short by one criterion, as it is believed to belong to the Kuiper Belt, an area of planetesimals, such as comets and asteroids, beyond the orbit of Neptune, which is probably what makes it even more of an interesting place to visit.

Although images of the Pluto-Charon System already exist, Tuesday 14^th July 2015 marks the day the world will discover Pluto’s features, with more detailed images of Pluto than currently exist produced by the New Horizons mission as it flies past. How exciting!

At 7h49m57s PDT, that’s 11h49m57s GMT, New Horizons will be at its closest approach to the Pluto-Charon system. Be sure to follow the #PlutoFlyby hashtag on Twitter, as well as the @NASANewHorizons Twitter account, as well as watching the live-stream on NASA TV from 7h30 EDT (11h30 GMT) or America Space from 6h00 EDT (10h00 GMT) for the latest updates on this once-in-a-lifetime event. I’m afraid you’ll have to wait until the next Moon Monday to hear about Phobos and Deimos but surely it’s worth it, as it’s Pluto’s turn to be in the limelight.

Live-stream: http://www.americaspace.com/?page_id=64931

Blog Post 2: Pluto: From Dwarf Planet To Superstar! Update

Hi everyone! Just giving you the NASA TV link for live coverage of the Pluto Flyby, as I don’t know if it’s just on my computer but the America Space link is not working. Don’t forget to be there by 7h49m57s EDT, that’s 11h49m57s GMT, to catch the closest approach of the Pluto Flyby. http://www.nasa.gov/multimedia/nasatv/index.html

Blog 3: Moon Monday: Mars’ Mysterious Moons Phobos & Deimos

Every reason why these moons should spark your curiosity.

The red planet has been the subject of our curiosity for decades now.  It has sparked the imagination of writers with sci-fi alien invasion film Mars Attacks and H.G. Wells’ War Of The Worlds novel.

In the real world, multiple efforts have been made to discover the origins, composition and potential for life of Mars’ surface. With 26 missions to its name (plus 30 failed missions), including the Mars Curiosity rover (which was launched in November 2011 to determine if Mars had ever able to support microbial life, gracing us with images of its polar ice caps and evidence of an ancient oasis on the surface) and plans for a human settlement on the planet in the future, these investigations continue and we continue to learn more about Mars. Meanwhile, its 2 moons Phobos and Deimos remain a mystery. So, what do we know and what has yet to be discovered?

Mars, named after the Greek god of war has 2 moons named Phobos & Deimos, meaning panic and flight. They were discovered by American astronomer Asaph Hall in August 1877 at the Naval Observatory in Washington D.C.. Phobos orbits Mars every 7.39 hours at a distance of 5989 km from Mars and Deimos orbits the planet every 30 hours 4 times as far away at a distance of 23460 km. For comparison, the Moon orbits the Earth every 28 days located 384400 km away. So, both of Mars’ moons are much closer to their host planet. In fact, Phobos’ orbit is closer than any moon in the solar system. As a result, for an observer at the polar region of Mars, the curvature of the planet would obscure the view of Phobos.

Phobos, the larger of the two moons is thought to have dimensions of 13 x 11.39 x 9.07 km. The non-spherical object has a heavily cratered surface. Scientists believe this could be as a result of impacts with other meteors or ejecta (debris) from the Martian surface below.

Deimos, the smaller of the 2 moons has a 6 km radius. While it is too light for gravity to squash it into a sphere, it has a more uniform shape and is nearer to spherical than Phobos. The asteroid of mass 1.8 x 10^15 kg and dimensions also boasts a heavily cratered surface with some very visible deep circular red rings and white rings at the polar regions. Its largest crater is about 2.3 km in diameter.

Despite being heavily cratered like Phobos, Deimos manages to look smoother partly due to its craters being filled with dust. Due to its mass, Deimos is too light to hold on to the dust produced by impacts. So, it is the gravity from the Martian surface below that keeps a ring of the dust around itself in about the same region as Deimos’ orbit. As the moon revolves, this dust is deposited over its craters. This means that using craters to calculate its age accurately would prove very difficult.

However, both moons have been estimated to be 4.5 billion years old. Their formation history and how they came to be in Mars’ orbit is still up for debate, but scientists have some ideas.

Phobos may have originated from elsewhere in the solar system, before passing near enough to Mars’ to be captured by its gravitational pull, unable to escape its orbit. One theory is that it is an object from the asteroid belt that was catapulted into Mars’ orbit by Jupiter’s orbit. The Phobos 2 mission supported this idea.

However, missions since suggest Phobos formed around Mars. Mars Express revealed the density of Phobos does not fit the capture scenario, because it is likely to have lots of interior space. Instead, Phobos will have formed from ejecta from Mars or from a collision between a previous Martian moon and another body. Scientists are not yet ruling out that Phobos was captured but its near-circular orbit and composition from primitive materials do point towards formation at Mars.

Deimos could be a captured asteroid.

Due to how comparatively small Mars’ moons are, they have very little effects on each other and Mars. In fact, Phobos creates a tiny tidal bulge on Mars of only a fraction of a millimetre.

Phobos is actually moving closer to the red planet by around 1.8 cm a year. Within 100 million years, it will crash onto Martian surface, creating a shower of debris, as it is ripped apart by the gravitational pull of the red planet. Some of this debris may also come together to form a ring around Mars.

Deimos is doing the opposite and is moving away from Mars. It will continue to do so until it is too far away for Mars’ gravitational pull to retain it in its orbit, leaving Mars moonless.

Before then, we have a lot more to discover about these moons. Scientists think Deimos is carbon-rich, with a mixture of ice and captured asteroids but we still need to know more about its interior. As both moons are too light to hang onto an atmosphere to protect them from the Sun’s UV radiation and impacts, we don’t expect life to be possible on these moons. However, analysing their surfaces more accurately may allow us to confirm how they formed. Deimos’ orbital path and formation history have yet to be uncovered.

The Phobos-Soil mission was set to collect information about the rotation, orbit and composition of Phobos but failed to launch in 2011. Future missions like Japan’s MMX in 2024 which will observe Phobos and Deimos and collect samples from Phobos, will shed more light on the Martian moons. It might even uncover just by how much Deimos is moving away from Mars per ear and when we should expect it to disappear from Mars’ orbit.