The place spacecraft go to die

The Tiangong I spacecraftImage copyrightCHINA MANNED SPACE ENGINEERING
Image captionChina’s Tiangong I spacecraft is expected to fall to Earth soon

China’s Tiangong-1 space station is currently out of control and expected to fall back to Earth next year. But not in the remote place where many other spacecraft end their days.

Explorers and adventurers often look for new places to conquer now that the highest peaks have been climbed, the poles reached and vast oceans and deserts crossed.

Some of these new places are called the poles of inaccessibility. Two of them are particularly interesting.

One is called the continental pole of inaccessibility – it’s the place on Earth furthest from the ocean. There is some debate as to its exact position but it’s considered by many to be near the so-called Dzungarian Gate – a mountain pass between China and Central Asia.

The equivalent point in the ocean – the place furthest away from land – lies in the South Pacific some 2,700km (1,680 miles) south of the Pitcairn Islands – somewhere in the no-man’s land, or rather no-man’s-sea, between Australia,New Zealand and South America.

This oceanic pole of inaccessibility is not only of interest to explorers, satellite operators are interested in it as well. That’s because most of the satellites placed in orbit around the Earth will eventually come down, but where?

Smaller satellites will burn up but pieces of the larger ones will survive to reach the Earth’s surface. To avoid crashing on a populated area they are brought down near the point of oceanic inaccessibility.

Scattered over an area of approximately 1,500 sq km (580 sq miles) on the ocean floor of this region is a graveyard of satellites. At last count there were more than 260 of them, mostly Russian.

The wreckage of the Mir space station lies there. It was launched in 1986 and was visited by many teams of cosmonauts and international visitors.

With a mass of 120 tonnes it was never going to burn up in the atmosphere, so it was ditched in the region in 2001 and was seen by some fishermen as a fragmenting mass of glowing debris racing across the sky.

Computer simulated images illustrate Mir's descent and break-up as it enters the Earth's atmosphereImage copyrightGETTY IMAGES
Image captionA computer-simulated image of Mir’s descent and break-up as it entered the Earth’s atmosphere in 2001

Many times a year the supply module that goes to the International Space Station burns up in this region incinerating the station’s waste.

No one is in any danger because of this controlled re-entry into our atmosphere. The region is not fished because oceanic currents avoid the area and do not bring nutrients to it, making marine life scarce.

One future visitor to this desolate place will be the International Space Station.

Current plans are for it to be decommissioned in the next decade and it will have to be carefully brought down in the oceanic pole of inaccessibility. With a mass of 450 tonnes – four times that of the Mir space station – it will make a spectacular sight.

Sometimes however, it’s not possible to bring a satellite or space station down in the South Pacific if ground controllers have lost contact with it.

A NASA image showing a graphical representation of space debris in low Earth orbitImage copyrightNASA
Image captionThe Earth is surrounded by thousands of pieces of space junk (dots not to scale)

Such a thing happened with the 36-tonne Salyut 7 space station in 1991 which came down in South America or the American Skylab that struck Australia in 1979. No one on the ground was injured, or indeed as far as we know, ever has been by a piece of falling spacecraft debris.

We will face that problem again next year.

Between January and April the Chinese Tiangong-1 will come back to Earth. It was launched in 2011 as China’s first space station. The following year it was visited by China’s first female astronaut, Liu Yang.

Tiangong-1’s orbit is decaying as it heads towards re-entry. But Chinese engineers have lost control of it and cannot fire its thrusters to bring it down in the South Pacific.

Instead it will come down somewhere between 42.8 degrees north and south. That’s between the latitude of northern Spain and southern Australia, and we won’t be able to be more precise than that until just a few hours before it burns up.

Tiangong-1 is one space station that probably won’t join its companions in the remote South Pacific.

Paris accord: US and Syria alone as Nicaragua signs

A man fishes in Cocibolca Lake in the province of Rivas, about 125km south of the capital Managua, on 4 November, 2013.Image copyrightAFP
Image captionNicaragua has been described as a “renewable energy paradise”

Nicaragua has signed the Paris climate agreement, meaning that the US and Syria are the only two countries not to be giving the accord their support.

The deal unites the world’s nations in tackling climate change.

Nicaragua refused to sign it last year, arguing that it did not go far enough to tackle the problem.

In June President Donald Trump said the US would withdraw from the deal, but the rules of the agreement state that this cannot be done until 2020.

The president said it was part of his “solemn duty to protect America” and he would seek a new deal that would not disadvantage US businesses.

Scientists point out that work to implement the Paris accord must be stepped up if it is to have any chance of success.

The agreement commits the US and 187 other countries to keeping rising global temperatures “well below” 2C above pre-industrial levels and “endeavour to limit” them even more, to 1.5C.

Farmer in a Nicaraguan coffee cropImage copyrightAFP
Image captionHighly sought-after Nicaraguan coffee is thought to be particularly susceptible to changes in weather patterns

Nicaraguan President Daniel Ortega indicated last week that he would sign the accord.

“It is time for Nicaragua to sign the Paris Agreement,” Mr Ortega said on the official July 19 website.

“Scientists from more developed countries, scientists working at Nasa, European scientists, everyone agrees that we must stop the process that is leading to the destruction of the planet,” he said.

Mr Ortega’s government had previously argued that the accord did not put sufficient onus on wealthy countries to tackle climate change and was not ambitious enough in its objectives.

Nicaragua has no oil and vigorously pursues green energy policies – more than 50% of its electricity is produced by geothermic, wind, solar, biomass and wave power. It is a country that is believed to be especially at risk from climate change.

Nicaraguan President Daniel Ortega (10 April 2015)Image copyrightAFP
Image captionNicaraguan President Daniel Ortega wants tough action to combat global warming

The World Bank described the central American country as “a renewable energy paradise” in 2013.

President Trump has argued that the Paris agreement would hobble, disadvantage and impoverish the US, to the benefit of other nations.

He claimed in June that the accord would cost the US 6.5 million jobs and $3tn (£2.2tn) in lost GDP – while rival economies like China and India were treated more favourably.

However, the US more recently has hinted that it may shift its position on withdrawing from the deal.

Historically, the US, Europe, and China account for almost half of the world’s carbon emissions.

Syria is thought not to have signed the deal because it has been preoccupied by its civil war.

More acidic oceans ‘will affect all sea life’

Cold water coralImage copyrightJAGO-TEAM/GEOMAR
Image captionCold water corals should be more resilient

All sea life will be affected because carbon dioxide emissions from modern society are making the oceans more acidic, a major new report will say.

The eight-year study from more than 250 scientists finds that infant sea creatures will be especially harmed.

This means the number of baby cod growing to adulthood could fall to a quarter or even a 12th of today’s numbers, the researchers suggest.

The assessment comes from the BIOACID project, which is led from Germany.

A brochure summarising the main outcomes will be presented to climate negotiators at their annual meeting, which this year is taking place in Bonn in November.

The Biological Impacts of Ocean Acidification report authors say some creatures may benefit directly from the chemical changes – but even these could still be adversely affected indirectly by shifts in the whole food web.

What is more, the research shows that changes through acidification will be made worse by climate change, pollution, coastal development, over-fishing and agricultural fertilisers.

Ocean acidification is happening because as CO2 from fossil fuels dissolves in seawater, it produces carbonic acid and this lowers the pH of the water.

Test tubesImage copyrightMAIKE NICOLAI/GEOMAR
Image captionMesocosms (“giant test tubes”) allow scientists to study acidification effects on real-world organisms

Since the beginning of the Industrial Revolution, the average pH of global ocean surface waters have fallen from pH 8.2 to 8.1. This represents an increase in acidity of about 26%.

The study’s lead author is Prof Ulf Riebesell from the GEOMAR Helmholtz Centre for Ocean Research in Kiel.

He is a world authority on the topic and has typically communicated cautiously about the effects of acidification.

He told BBC News: “Acidification affects marine life across all groups, although to different degrees.

“Warm-water corals are generally more sensitive than cold-water corals. Clams and snails are more sensitive than crustaceans.

“And we found that early life stages are generally more affected than adult organisms.

“But even if an organism isn’t directly harmed by acidification it may be affected indirectly through changes in its habitat or changes in the food web.

“At the end of the day, these changes will affect the many services the ocean provides to us.”

On the agenda

Since 2009, scientists working under the BIOACID programme have studied how marine creatures are affected by acidification during different life stages; how these reactions reverberate through the marine food web; and whether the challenges can be mitigated by evolutionary adaptation.

Some research was done in the lab but other studies were conducted in the North Sea, the Baltic, the Arctic, and Papua New Guinea.

A synthesis of more than 350 publications on the effects of ocean acidification – which will be given to climate delegates at next month’s summit – reveals that almost half of the marine animal species tested reacted negatively to already moderate increases in seawater CO2 concentrations.

Early life stages were affected in Atlantic cod, blue mussels, starfish, sea urchins and sea butterflies.

But an experiment with barnacles showed they were not sensitive to acidification. And some plants – like algae which use carbon for photosynthesis – may even benefit

Dr Carol Turley, an ocean acidification expert from Plymouth Marine Labs in the UK described the BIOACID research as enormously important.

She told BBC News: “It’s contributed enormous insights into the impacts that acidification can have on a wide range of marine organisms from microbes to fish.

“It’s also explored how in combination with ocean warming and other stressors it might play out at the ecosystem level and affect human society.

“On the lead-up to the UN climate change negotiations in Bonn this November it is clear that the ocean and its ecosystems should not be ignored.”

The conference is being held in Germany but it is being chaired by Fiji, which wants delegates to give due prominence to the effects of CO2 on the ocean.

Astrolabe: Shipwreck find ‘earliest navigation tool’

AstrolabeImage copyrightPHILIP KOCH
Image captionThe instrument was once used by mariners to measure the altitude of the Sun during their voyages

An artefact excavated from a shipwreck off the coast of Oman has been found to be the oldest known example of a type of navigational tool.

Marine archaeologists say the object is an astrolabe, an instrument once used by mariners to measure the altitude of the Sun during their voyages.

It is believed to date from between 1495 and 1500.

The item was recovered from a Portuguese explorer which sank during a storm in the Indian Ocean in 1503.

The boat was called the Esmeralda and was part of a fleet led by Portuguese explorer Vasco da Gama, the first person to sail directly from Europe to India.

David Mearns, from Blue Water Recovery, who led the excavation and is the author of The Shipwreck Hunter, told the BBC: “It’s a great privilege to find something so rare, something so historically important, something that will be studied by the archaeological community and fills in a gap.”

The astrolabe was discovered by Mr Mearns in 2014, and was one of nearly 3,000 artefacts recovered during a series of dives.

The bronze disc measures 17.5cm in diameter and is less than 2mm thick.

“It was like nothing else we had seen and I immediately knew it was something very important because you could see it had these two emblems on it,” said Mr Mearns.

“One I recognised immediately as a Portuguese coat of arms… and another which we later discovered was the personal emblem of Don Manuel I, the King of Portugal at the time.”

The excavation team believed the object was an astrolabe, but they could not see any navigational markings on it.

However, a later analysis uncovered its hidden details.

Laser scanning work carried out by scientists at the University of Warwick revealed etches around the edge of the disc, each separated by five degrees.

Astrolabe laser scan

This would have allowed mariners to measure the height of the sun above the horizon at noon to determine their location so they could find their way on the high seas.

Mariners’ astrolabes are relatively rare, and this is only the 108th to be confirmed catalogued. It is also the earliest known example by several decades.

Mr Mearns said: “We know it had to have been made before 1502, because that’s when the ship left Lisbon and Dom Manuel didn’t become King until 1495, and this astrolabe wouldn’t have carried the emblem of the King unless he was King.

“I believe it’s probably fair to say it dates roughly to between 1495 to 1500. Exactly what year we don’t know – but it is in that narrow period.”

He added: “It rolls back this history by at least 30 years – it adds to evolution, it adds to the history, and hopefully astrolabes from this period can be found.”