Mercury

There’s a Complex History of Skin Lighteners in Africa and Beyond

The long history of racist beauty standards alone cannot explain the ongoing global use of harmful skin lighteners.

Somali-American activists recently scored a victory against Amazon and against colourism, which is prejudice based on preference for people with lighter skin tones. Members of the non-profit The Beautywell Project teamed up with the Sierra Club to convince the online retail giant to stop selling skin lightening products that contain mercury.

After more than a year of protests, this coalition of antiracist, health, and environmental activists persuaded Amazon to remove some 15 products containing toxic levels of mercury. This puts a small but noteworthy dent in the global trade in skin lighteners, estimated to reach $31.2 billion by 2024.

What are the roots of this sizeable trade? And how might its most toxic elements be curtailed?

The online sale of skin lighteners is relatively new, but the in-person traffic is very old. My new book explores this layered history from the vantage point of South Africa.

As in other parts of the world colonised by European powers, the politics of skin colour in South Africa have been importantly shaped by the history of white supremacy and institutions of racial slavery, colonialism, and segregation. My book examines that history.

Yet, racism alone cannot explain skin lightening practices. My book also attends to intersecting dynamics of class and gender, changing beauty ideals and the expansion of consumer capitalism.

A deep history of skin whitening and lightening

For centuries and even millennia, elites used paints and powders to create smoother, paler appearances, unblemished by illness and the sun’s darkening and roughening effects.

Cosmetic users in ancient Mesopotamia, Egypt, Greece, and Rome created dramatic appearances by pairing skin whiteners containing lead or chalk with black eye makeup and red lip colourants. In China and Japan too, elite women and some men used white lead preparations and rice powder to achieve complexions resembling white jade or fresh lychee.

Skin lighteners generate a less painted look than skin whiteners by removing rather than concealing blemished or melanin-rich skin. Melanin is the biochemical compound that makes skin colourful.

Active ingredients in skin lighteners have ranged from acidic compounds like lemon juice and milk to harsher chemicals like sulfur, arsenic, and mercury. In parts of precolonial Southern Africa, some people used mineral and botanical preparations to brighten – rather than whiten or lighten – their skin and hair.

During the era of the trans-Atlantic slave trade, skin colour and associated physical difference were used to distinguish enslaved people from free, and to justify the former’s oppression. Colonisers cast melanin-rich hues as the embodiment of ugliness and inferiority. Within this racist political order, some sought to whiten and lighten their complexions.

By the twentieth century, mass-produced skin lightening creams ranked among the world’s most popular cosmetics. Consumers included white, black, and brown women.

In the 1920s and 1930s, many white consumers swapped skin lighteners for tanning lotions as time spent sunbathing and playing outdoors became a sign of a healthy and leisured lifestyle. Seasonal tanning embodied new forms of white privilege.

Skin lighteners became primarily associated with people of colour. For black and brown consumers, living in places like the United States and South Africa where racism and colourism have flourished, even slight differences in skin colour could carry political and social consequences.

The mercury effect

Skin lighteners can be physically harmful. Mercury, one of their most common active ingredients, lightens skin in two ways. It inhibits the formation of melanin by rendering the enzyme tyrosinase inactive; and it exfoliates the tanned, outer layers of the skin through the production of hydrochloric acid.

By the early twentieth century, pharmaceutical and medical textbooks recommended mercury – usually in the form of ammoniated mercury – for treating skin infections and dark spots while often warning of its harmful effects. Cosmetic manufacturers marketed creams containing ammoniated mercury as “freckle removers” or “skin bleaches”.

When the US Congress passed the Food, Drug and Cosmetics Act in 1938, such creams were among the first to be regulated.

After World War II, the negative environmental and health impact of mercury became more apparent. The devastating case of mercury poisoning caused by industrial wastewater in Minamata, Japan, prompted the Food and Drug Administration to take a closer look at mercury’s toxicity, including in cosmetics. Here was a visceral instance of what environmentalist Rachel Carson meant about small, domestic choices making the world uninhabitable.

In 1973, the administration banned all but trace amounts of mercury from cosmetics. Other countries followed suit. South Africa banned mercurial cosmetics in 1975, the European Economic Union in 1976, and Nigeria in 1982. The trade in skin lighteners, nonetheless, continued as other active ingredients – most notably hydroquinone – replaced ammoniated mercury.

Meanwhile in South Africa

In the early 1960s, colour photography and printing saw skin lightener ads feature a range of light brown and reddish skintones.

In apartheid South Africa, the trade was especially robust. Skin lighteners ranked among the most commonly used personal products in black urban households. During the 1980s, activists inspired by Black Consciousness and the sentiment “Black is Beautiful” teamed up with concerned medical professionals to make opposition to skin lighteners part of the anti-apartheid movement.

In the early 1990s, activists convinced the government to ban all cosmetic skin lighteners containing known depigmenting agents – and to prohibit cosmetic advertisements from making any claims to “bleach”, “lighten” or “whiten” skin. This prohibition was the first of its kind and the regulations immediately shuttered the in-country manufacture of skin lighteners.

South Africa’s regulations testify to the broader antiracist political movement from which they emerged. Thirty years on, however, South Africa again possesses a robust – if now illicit – trade in skin lighteners. An especially disturbing element is the resurgence of mercurial products.

South African researchers have found that over 40% of skin lighteners sold in Durban and Cape Town contain mercury.

The activists’ recent victory against Amazon suggests one way forward. They took out a full-page ad in a local newspaper denouncing Amazon’s sale of mercurial skin lighteners as “dangerous, racist, and illegal.” A petition with 23,000 signatures was hand-delivered to the company’s Minnesota office.

By combining antiracist, health, and environmentalist arguments, activists held one of the world’s most powerful companies accountable. They also brought the toxic presence of mercurial skin lighteners to public awareness and made them more difficult to purchase.

Lynn M. Thomas’s latest book Beneath the Surface: A Transnational History of Skin Lighteners is available from Wits University Press and from Duke University Press.

Lynn M. Thomas, History Professor, University of Washington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Did You Know? On Average, Mercury Is Earth’s Closest Neighbour.

Trying to improve stargazing and space-journeying are lofty goals but we often forget that pursuing and celebrating curiosities are valuable, too.

Which planet is closest to Earth? Common sense suggests it’s Venus or Mars, and common sense would be right. However, technically speaking, this isn’t entirely true. At different points in their respective orbits, Earth, Venus and Mars are at different distances from each other. Out of curiosity, if these variations in distance were factored in, which planet would be closest?

The answer is weird: it’s Mercury.

Point-circle method (PCM) is a technique that averages the distance between every point on a planet’s orbit and every point on the second planet’s orbit. Using this, three researchers found that Venus is on average is 1.14 astronomical units (AU) away from Earth and Mercury is 1.04 AU away.

The researchers figured that for any two bodies in the same plane and moving in concentric orbits, the average distance between the two bodies is directly proportional to the radius of the inner orbit.

To validate this corollary, they plotted the planets in their actual elliptical orbits in 3D and ran a simulation for 10,000 years. The simulation recorded the distances between each pair of planets every 24 simulation hours.

The average measured distances deviated from the results from PCM by less than 1% – so their calculation was right. On average, Mercury is Earth’s closest neighbour.

To be completely honest, this isn’t entirely useful information. The researchers’ finding doesn’t change how astronomers and spaceflight planners work. In fact, it could even be a case of ‘data torture’: analysing a large dataset in multiple ways and finding one interesting result – the statistical equivalent of a broken clock being right twice a day.

One astrophysicist told The Wire, “Any physical quantity is interesting to the degree to which it determines the solution of interesting questions. For planetary dynamics, some of the interesting questions are about the evolution of the orbits of the planets, satellites, asteroids, comets and other minor bodies. The physical quantities of interest are the Keplerian orbital elements, whose long-time evolution is in general difficult to calculate.”

In this picture, the “average distance” the researchers have calculated – the astrophysicist said – might not be worthwhile. “Further discussion on this topic may enliven casual conversation but writing more about it could be, in my opinion, a waste of time.”

These are sobering words. However, the researchers’ article does have one very important redeeming quality. Trying to improve stargazing and space-journeying are lofty goals but we often forget that pursuing and celebrating curiosities are valuable, too. So knowing that Mercury is in a certain way closer to Earth is – to name that quality – wow. And wow needn’t be a waste of time.

Pratik Pawar is a science writer and a recipient of the S. Ramaseshan science writing fellowship.

NGT Committee Finds Sterlite Violated Laws but Pleads for Leniency

Even though there is no dispute that an offence has occurred, the committee believes that the violation of the principles of natural justice is sufficient grounds to absolve Sterlite of its crimes.

Contrary to various media reports, the Tarun Agarwal Committee report actually confirms the allegations the Tamil Nadu Pollution Control Board (TNPCB) and public interveners had levelled against Sterlite Copper.

The Wire has obtained a copy of the report. It explicitly finds the company guilty of violating statutory conditions on several counts. These findings don’t only contradict news reports that suggested Sterlite had been given a clean chit. They also differ from the recommendations the committee made in conclusion.

In fact, the committee has agreed with many of the TNPCB’s allegations, including illegal operation by Vedanta, the group that manages Sterlite Copper. However, the committee has asked for leniency when dealing with them. It also says the TNPCB violated the principles of natural justice and calls for reopening the factory.

This is curious. It suggests that even if there is no dispute that an offence has occurred, the committee believes that the violation of the principles of natural justice is sufficient grounds to absolve the accused of the crime!

Also read: Some Questions About Justice Goel’s Tenure at the NGT

Further, the violations – under the Air Act, Water Act and Hazardous Waste Rules – contain no caveats for lenient treatment of violators.

The irony deepens when considering the victims’ plight. These victims include the people of Tuticorin affected by the unlicensed and substandard operation of a polluting industry. In this instance, the only parties representing the people of Thoothukudi – the interveners – have been denied an independent legal status by the National Green Tribunal (NGT).

Their request for a copy of the Agarwal Committee’s report was also turned down, and they were directed to assist the state counsel without official access to it.

Rejection of consent to operate

The appeal filed by Vedanta Ltd. assails the TNPCB’s order dated April 9, 2018, rejecting the company’s request for renewal of an operating license under the Air and Water Acts. The latter require the TNPCB to deny a license if the company fails to comply with conditions detailed in the Acts.

The April 9 order is based on five alleged violations of license or consent conditions by the company (quoted verbatim, lightly edited for clarity):

Groundwater analysis report taken from borewells within the unit premises as well as surrounding areas have not been furnished to ascertain the impact on groundwater quality.
The unit has not removed the copper slag dumped/stored along the river Uppar and patta land, thereby obstructing the flow. It has also not constructed any physical barrier between river Uppar and slag land fill area of patta land so as to prevent slag from reaching the river.
Authorisation issued to the unit on July 10, 2008, got expired on July 9, 2013, but the unit continued to generate and dispose hazardous waste without valid authorisation under Hazardous and Other Wastes (Management & Transboundary Movement) Rules, 2016. The application submitted by the unit was returned for want of additional details and the unit had not resubmitted the same.
As per renewal condition, the unit should have analysed the parameters of heavy metals such as arsenic in the ambient air through the board’s laboratory as done for the other parameters such as NOx, PM 10 and SO2. As the board laboratory does not have this facility, the unit should have engaged the services of MoEF&CC/NABL accredited laboratories and furnished the report to the board. The unit has not complied with the same and as such there is no authenticated reporting on the presence of arsenic in the ambient air.
During the inspection on February 22, 2018, the unit was directed to construct a gypsum pond as per CPCB guidelines. But the unit had not complied till March 31, 2018.

The committee has confirmed that Sterlite committed three of these alleged violations. The committee also found Sterlite had failed to maintain an adequate greenbelt and operated with a lower-than-required chimney stack.

We quote directly from the report to highlight Sterlite’s violations.

Allegation 1: Sterlite failed to submit independent monthly reports to the TNPCB analysing heavy-metal content in water samples.

Para 100 of the committee report: “… responsibility has been given to the TNPCB as well as to appellant to monitor groundwater quality independently. As per condition number 44, the appellant is required to analyse the groundwater quality on their own once a month and furnish the report to the TNPCB periodically. This apparently has not been done by the company.”

Allegation 2: Sterlite failed to remove copper slag from the banks of the Uppar river despite several reminders. As a result, the river’s flow has become obstructed.

Para 117: “In this regard, the committee inspected the spot and found that 3.5 lakh metric tonnes of copper slag has been dumped over the alleged patta land…”

Para 119: “The appellant company could not have sold slag more than what was required to fill up the low-lying area. The quantity sold in excess was wholly inappropriate. The contention of the appellant that it is not their responsibility to remove the copper slag is erroneous. The committee is of the opinion that the retaining wall so constructed was inadequate and in any case copper slag could not have been dumped next to the Uppar river. It is the responsibility of the appellant company to ensure that the copper slag is put to beneficial use and is not dumped haphazardly.”

Also read: As Sterlite Plant Expands, a City Erupts in Protest

Para 120: “The filling of low-lying area means that the low-lying area has to be filled upto the ground level. In the instant case, raising the height of the land upto the level of a four-lane highway is not permissible and is not the intention as per the consent orders to fill up the low-lying area. Low-lying area means the area below the ground level…

“The committee finds that the copper slag should not have been dumped next to the river side and therefore, is required to be removed completely. Further, the slag is of fine granular material, finer than sand, and tends to blow into the atmosphere whenever there is a strong wind blowing…

“However, closure of the factory on this ground itself seems to be harsh even though show-cause notices dated March 14, 2017, and dated September 11, 2017 … were issued by the TNPCB.”

Para 124: “The contention of the appellant company, that no permission was required to be taken from the TNPCB for disposal of the copper slag, is patently erroneous. In this regard, the committee finds that the consent order dated October 5, 2012, … specifically stipulates in condition no. 10 that the company would take approval from the concerned agency for disposal of the slag.”

Para 126: “This fact has not been denied by the company and a feeble argument was raised that the copper slag was sold to private parties for land fill, but such claim has not been backed by any evidence. Apparently, the company has dumped the copper slag blatantly in violation of the consent orders.”

Allegation 3: Since the company’s license to handle hazardous wastes expired in 2013, the company was generating and disposing hazardous wastes illegally without proper … authorisation under the Hazardous Waste Rules.

Para 129: “One gets an uncanny feeling that neither the appellant was interested in having the authorisation under the Rules of 2016 nor was the TNPCB keen to either issue the authorisation letter or to reject the application. Further, the committee finds it strange to note that whereas lot of noise has been raised by the TNPCB that the company has continued to dispose of hazardous waste for more than 58 months without taking a valid authorisation under the relevant Rules, … the board continued to give consent to the appellant to operate the unit. In the opinion of the committee, it is not open to the TNPCB to blow hot and cold at the same time…

“The committee is of the opinion that in the current scenario both the appellants and the pollution board are responsible equally for keeping the application pending…

“In this regard, the committee is of the opinion that under the consent orders it is one of the mandatory conditions that the company is required to dispose of the waste as per the Rules of 2016.”

Also read: Sterlite Plant Will Not Be Re-Opened, Tamil Nadu Government Says

Additional grounds

The public interveners and the TNPCB made several other allegations during the committee’s hearings in Chennai. They included fraudulent claims relating to available land, an inadequate greenbelt and low chimney stacks. While the committee didn’t arrive at conclusions about the available land, it did vis-à-vis the other two complaints.

Allegation 4: Violation of the greenbelt condition

Para 160: “At the time of physical inspection of the unit, the committee noticed that there was hardly any greenery inside the factory premises and that it was a concrete jungle except the area between main gate and the administrative section where a garden with palm trees was developed.

“The company may have developed a green area in its township, but that cannot be included the cover the green belt inside the factory premises. The condition that the company is required to develop 25 m width of green belt around the battery limits of the factory has not been adhered to by the company.”

Allegation 5: Sterlite’s chimney stack is not high enough, leading to ineffective dispersion of air pollutants.

Para 178: “Thus, according to the opinion of the committee based on load-basis standards at 2.0…, the stack height would be 83.51 m. If load-basis standards at 1.0 is applied, then the stack height would be 67.83 m, whereas the present stack is 60.38 m [high], i.e. below prescribed limits.”

Para 179: “The reason for evaluating the height of the stack becomes necessary in light of the continuous complaints being made by the interveners, by the TNPCB and by the residents of Tuticorin, alleging eye irritation, skin disorder, throat suffocation, asthma, etc. If the stack height is increased, SO2 and other gases will get diluted in the atmosphere and will not affect the inhabitants of Tuticorin, nor would such noxious gases affect the livestock.”

Nityanand Jayaraman is a Chennai-based writer and social activist and has been involved in the campaign against Sterlite Copper’s pollution.

Dear Minister: An Indian Did Try to Fly But He Definitely Didn’t Invent the Aeroplane

If the thinking of Satya Pal Singh is anything to go by, we must prepare for a long spell of darkness.

Satya Pal Singh. Credit: PTI

Success is a strange thing. It is one moment in a long and arduous journey of enterprise. It is Sachin Tendulkar’s 100th century alone but not the 99 centuries that came before. It is Thomas Edison & co.’s famous incandescent lightbulb and not the 6,000+ attempts that came before in search of the right materials. Success is a brief flaring up of the candle of perseverance before it settles back down and keeps glowing. To put it out after that moment maybe fair to the flare, but it’s not fair to the candle.

When Satya Pal Singh, the minister of state for human resource development, says that engineers must be taught the story of an Indian who flew an airplane eight years before the Wright brothers’ feat, he is blowing his nose over that candle. Singh is blinkered by his lust for Indian supremacy so much so that he is fixated on an Indian, a Mumbaikar, flying an airplane in 1895 – an event that may not have happened – and ignores the enterprise that must have come before, and the encouragement that should have come after.

The Mumbaikar in question is Shivkar Bapuji Talpade. According to some reports, Talpade built an airplane when we was an instructor at the city’s Sir J.J. School of Art. It seems he had been inspired by supposedly descriptions of airplanes in Hindu mythology in the Vaimanika Shastra, an exposition of the sage Bharadwaja, and wanted to recreate them. Anecdotal reports compiled by Pratap Velkar, an architect-historian, suggest that on the day of the flight, few were in attendance. However, another report – filed by an author named K.R.N. Swamy in the Deccan Chronicle – suggests that the then-king of Baroda was in the audience.

This contradiction is trivial compared to what came after. According to Velkar and Swamy both, Talpade’s airplane stayed airborne for a few minutes, flying over 1,500 feet before dropping down. The source of energy during this feat was allegedly a ‘mercury vortex engine’: a drum of mercury that, when exposed to sunlight, released hydrogen and buoyed the plane up.

Mercury does not react with sunlight, although it could participate in sunlight-induced chemical reactions. It reacts only moderately with oxygen, so it’s not clear where the hydrogen comes from. More importantly, Swamy claims in his article that Talpade’s airplane was able to produce enough thrust to lift a presumably 200-kg airplane into the air and propel it across 1,500 feet. Velkar disputes this. Finally, Velkar and Swamy both speak of an unmanned aircraft while Singh has said that Talpade flew the thing. It would seem the latter is not even wrong.

These descriptions, and others besides, have been thoroughly bunked – especially by those scientific traditions of the West that Satya Pal Singh is reluctant to agree with. The clincher is that if Talpade’s feat did actually happen the way chroniclers have said it did, then anyone today building an airplane with the same principles should be able to recreate it. This hasn’t been possible.

All of this also misses the point. According to Velkar, after Talpade completed his demonstration on an unmarked day in 1895, he wasn’t able to raise enough funds, neither from the king of Baroda nor from other businessmen, to build a second aircraft. State help was not forthcoming. When Velkar eventually tracked down the research papers written by Talpade to the possession of a scientist named G.H. Bedekar, Bedekar said that the papers only reveal that Talpade had failed in his efforts.

We should not teach our students that Talpade flew an airplane. In the absence of concrete evidence, we shouldn’t even teach them that Talpade succeeded because it is only a disputed moment of success. We should teach them that Talpade tried, which is more important. To build a candle in the dark of our ignorance that flares briefly, controversially, and then dies is useless. Our students must be equipped to build candles that glow and glow.

As Aparajith Ramnath, a historian of science, wrote in The Wire, “To reduce [research] to a battle for priority is to replace an intricate portrait with a gross caricature.”

The point of teaching ‘ancient technology’, if it happens, should be to inculcate the spirit of perseverance and entrepreneurship. A Shivkar Bapuji Talpade today ought to be able to try and fail, and not have the consequence of such failure bog her down for the rest of her life. Moreover, the value of good research is born out of an invaluable global contract. For example, the value of the contract between two scientists working in separate labs is born out of using the scientific method to perform their experiments just like the value of a 100-rupee bill is born out of an economic contract between the citizens of a country and the state.

Sidestepping these contracts to create our own value system will take us nowhere – neither further into knowing our past better nor shaping the future. However, it is easily possible to simultaneously acknowledge value-systems of the past, and the intellectual and socio-political contexts in which they operated. So to acknowledge that Oliver and Wilbur Wright flew an airplane for the first time in 1903 is to acknowledge a contract that scientists and engineers abide by to this day: that the plane can be recreated, that it will fly just as the brothers and other historians have described, that it will bank on scientific principles that have been validated over and over. But to suggest that it hegemonises the contracts forged by ancient Indian traditions is misguided.

It does not, and herein lies the fallacious derision of the West that a part of the modern, post-colonial India is given to. To describe ‘success’ in the form of an airplane that flew according to natural contracts described thousands of years ago and to describe ‘success’ as improving research quality in the global arena today typifies the conflict that Singh and others like him have been unable to overcome. This is the conflict that prevents India from transitioning from an erstwhile giver of knowledge to a modern taker, a conflict that a historian would simply dismiss as ‘presentism’.

We must become okay with taking so we can be givers again. We can’t give from the past to a world that has moved on.

In the same vein, improving India’s research output, both in quantity and quality, requires a state that acknowledges the environmental shift in which our contracts have operated. It requires a state that provides ample funds for research that abides by prevailing global contracts, ensures that those funds reach researchers on time and are utilised effectively – instead of letting talent descend into ignominy the way Talpade has. It requires a state that is willing to wait for research to ripen, that remains cognisant of the value of burning candles before sniffing and grumbling in the absence of a flare.

If the thinking of Satya Pal Singh is anything to go by, we must prepare for a long spell of darkness.

Earthlings Watch as Tiny Mercury Sails Past the Sun

A jet airliner leaves a vapour trail as the planet Mercury is seen, lower left quadrant, transiting across the face of the sun in Las Vegas, Nevada, May 9, 2016. Credit: REUTERS/David Becker

CAPE CANAVERAL, Fla.: Tiny Mercury, the solar system’s innermost planet, sailed across the face of the sun on Monday, a celestial dance that occurs about once every decade as Earth and its smaller neighbouring planet align in space.

The journey, which astronomers refer to as a “transit,” began with what looked to be a small, black dot on the edge of the sun at 7:12 a.m. EDT (1112 GMT), images relayed live on NASA TV showed.

Over the next seven and a half hours, Mercury, which travels at a speed of 30 miles (48 km) a second, crossed the face of the sun, a spectacle last seen in 2006.

“It’s all about perspective,” NASA planetary sciences chief Jim Green said during a panel discussion aired on NASA TV.

Mercury’s orbit around the sun is more tilted than Earth’s so it only rarely appears to cross the sun relative to Earth’s line of sight, Green said.

About 13 times a century, Mercury and Earth line up, giving armchair stargazers and professional astronomers a chance to view Mercury as it passes between Earth and the sun.

Monday’s transit was the first since NASA’s MESSENGER mission to Mercury, which orbited the planet from 2011 to 2015. The spacecraft relayed startling details of Mercury’s heavily cratered and unexpectedly diverse landscape.

Though temperatures on Mercury’s surface reach 800 degrees Fahrenheit (427 degrees Celsius) – hot enough to melt lead – the planet also has deep craters where the sun never shines. These pits, where temperatures rival the coldest places in the solar system, contain frozen water and organic materials.

During Monday’s transit, astronomers hope to build on MESSENGER’s findings by learning more about gases vaporizing from the planet’s surface. The “out-gassing” may be a factor in why Mercury is shrinking, Green said.

Astronomers also used the transit to calibrate sensors on a trio of space-based solar telescopes and refine techniques to look for planets beyond the solar system.

“When a planet crosses in front of the sun, it causes the sun’s brightness to dim. Scientists can measure similar brightness dips from other stars to find planets orbiting them,” NASA said.

Mercury will pass between the sun and Earth again in 2019. After that, the next opportunity to witness the event will not come until 2032.

(Reporting by Irene Klotz; Editing by James Dalgleish)

Mercury: ‘First Rock From the Sun’ in Transit

In every century there are only 13 or 14 transits of Mercury and you have to be on the right part of the globe if you want to watch a particular transit from beginning to end, which usually lasts for several hours.

Mercuy’s Caloris basin, seen in exaggerated colour. At 1,525km diameter this is the largest impact basin on the planet. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The solar system’s smallest and most remarkable planet, Mercury, will cross the face of the sun on May 9 – offering a great opportunity for people in many places across the world to see it.

Mercury is a dark and enigmatic world, which bears the scars of a strangely long history of volcanic eruptions and tectonic activity. Its crust is unreasonably rich in elements that normally easily evaporate from the surface, such as sulphur, sodium and potassium. This is odd, as these are the kind of substances that are most likely to have been lost during a hot and violent birth such as Mercury’s.

Mercury scoots round the sun in only 88 days, overtaking the more sedately moving Earth every three or four months. Because Mercury’s orbit is tilted at about seven degrees with respect to the Earth’s, it passes directly between us and the sun (a transit) only when both it and the Earth are close to the points where their orbital planes intersect. This can happen only in early May or early November.

In every century there are only 13 or 14 transits of Mercury and you have to be on the right part of the globe if you want to watch a particular transit from beginning to end, which usually lasts for several hours. If it starts soon after sunset it is likely to be finished before dawn, meaning you won’t catch any of it. However the May 9 afternoon transit is perfectly timed for viewing the entire thing from Europe and most of the Americas.

Mercury’s transits are more common than those of Venus, which comes in a pair eight years apart then separated by intervals of more than a century. The previous transit of Mercury (November 8, 2006) happened while the sun was below the horizon from Europe, India and anywhere in between, so many sky watchers are particularly keen to see this one for themselves. Interest has been heightened by the surprises revealed by NASA’s recent MESSENGER mission, including that its earliest crust was made of graphite, unlike the other rocky planets.

Historic observations

The first planetary transit ever to be observed was in fact one of Mercury in 1631, when the French astronomer Pierre Gassendi saw it by using a telescope to project an image of the sun onto the wall of a darkened room. Eight years later Englishman Jeremiah Horrocks used the same technique when he became the first to see a transit of Venus. Projection was the only safe way to do it, because a telescope collects heat as well as light, and even today nobody should try to look at the sun through a telescope unless there is a purpose-built solar filter across the main aperture.

On November 7, 1677, Edmond Halley (he of comet fame) documented a transit of Mercury from the South Atlantic island of St Helena. It dawned on him that the slightly different perspective from vantage points in various parts of the globe would cause a transiting planet to take a slightly different track across the sun in each case. The most precise way to determine this would be to measure exactly how long the transit lasted as seen from each site, and the data could then be used to work out the distance between the Earth and the sun, which had not yet been satisfactorily achieved.

In fact Venus, being larger and closer to the Earth, gives a more precise measure, and thanks to Halley’s insight French and British expeditions were mounted to various remote parts of the globe for its 1761 and 1769 transits. For example, the main impetus behind Captain Cook’s first round the world voyage was to observe the 1769 transit of Venus from Tahiti. A few months later he also observed a transit of Mercury while ashore in New Zealand, at a place that he named Mercury Bay.

There’s little new science that we can get out of observing a transit of Mercury these days, but the European Space Agency is inviting schools to submit their transit timing observations to derive their own measurement of the Earth-sun distance.

Transit viewing

The May 9 transit will begin at 12:12 BST and end at 19:42 BST, which could hardly be more convenient for viewing from western Europe. Those in India will be able to watch for an hour or two before the sun sets whereas people on the east coast of North America will have to rise early to catch the start. However, people living in Japan and Australia will miss the whole thing.

The next transit of Mercury after this will be 12:35 to 18:04 GMT on November 11, 2019, but in the UK sunset happens well over an hour before the end. After that there’s a long wait until November 2032.

Unlike Venus, Mercury is too small to see against the sun without magnification, and it can be dangerous to try due to the sun’s glare. So my advice is to go to an organised transit viewing event – many astronomy clubs and universities are organising these. Another option is to view it online. The European Space Agency will be webstreaming live images from space (no clouds in the way) and from solar telescopes in Spain and Chile.

David Rothery, Professor of Planetary Geosciences, The Open University

This article was originally published on The Conversation. Read the original article.