Category Archives: Science

Water management in Space Settlements

Humans need water to survive, and hence a reliable water supply is essential for Space Settlements. Fortunately Near Earth Objects consist for a substantial part of water. However human and industrial consumption of water produces waste water. Though we could “dump” this into space and replace it with fresh water from NEOs, that would be quite inefficient, and it also limites the growth of Space Settlements in the long run. Consequently we need to recycle water in Space habitats.

Basically we need a closed loop in which waste water is turned back into drinkable water. Hence a reliable and preferably cheap method of water purification is essential for the successful humanization of space.

A potentially promising method seems to be found. According to this article in the Science Daily, graphene is an excellent water filter. Not only is this method fast, it is also not energy intensive, and scientists hope to be able to turn seawater into freshwater just by using a hand pump with this graphene filter in the near future.

Nowadays graphene can be produced easily, and it is an allotrope of carbon, an element very abundantly in Near Earth Asteroids.

On a side note, we could wonder whether graphene filters can be used for extracting uranium from seawater. Though the concentration of uranium in seawater is low, the total amount of uranium in the oceans far exceed to total known reserves on land. But due to the concentration of uranium in seawater many scientists believe, extraction from seawater will be impracticable, at least with current market prices.

According to the Science Daily article, graphene filters can accurately distinguish between  difference in atomic seizes. This would be important if we want to filter out uranium atoms from seawater.

Probably we would need two filters: one the filter out atoms and molecules larger than uranium, and a second filter which on let smaller atoms and molecules through. Consequently the uranium atoms will get trapped between the two filters, and with each cycle the concentration of uranium will increase.

If this procedure will be feasible, then most countries will be able to become self-sufficient in their uranium supply. Currently only a few countries dominate the world market.

Interstellar space and resources

In reference to our recent post on generation ships, a commenter addressed an important issue: the amount of resources in interstellar space. Most people will probably know that the Solar System contains enormous amounts of resources. But it’s a common perception that space between stellar systems is very empty.

Emptiness is space is, of course, a very relative concept. A cubic meter of average interstellar space does contain much less matter than the best human made matter. This is mainly due to the very large distances between material objects in outer space.

But an important question is where does interstellar space start, or more accurately what are the boundaries of our Solar System? Unfortunately this is not a question with a definite answer. Basically there are two “popular” ideas of what constitutes the boundary of our Solar System: the heliopause and the Oort cloud.

When last summer it was announced that the Voyager 1 had “left” our Solar System, scientist referred to the fact that this space probe that crossed the heliopause. But what is the heliopause? The heliopause is the outer-boundary of the heliosphere, which turns us to the question what is the heliosphere?

Consider this analogy: if you let water flow from your tap into the sink, you will notice there is a kind of “gap” in the layer of water at the bottom of the sink. A similar thing happens with the Sun. The Sun emits constantly all kind of stuff, the so-called Solar winds. We can compare the Sun with your tap, and the Solar winds with the water flowing out of the tap. But just in case of your tap, the Solar wind will ultimately encounter a “thick” medium, and this medium is called the heliosphere. The inner-boundary, where the Solar wind is slowed down, is known as the termination shock. But after a certain distance this thick medium will end, which creates an outer-boundary for the heliosphere: the heliopause.

Because the Solar winds are effectively terminated at the heliopause, many scientists see this mark as the boundary of our Solar System.

The heliopause is located at approximately 119 astronomical units or AU (1 AU is equal to the average distance between the Sun and the Earth) from the Sun. In comparison the orbit of Pluto is located between 30 and 49 AU. Pluto is now considered to be a member of the so-called Kuiper belt, a collection of Trans-Neptunian Objects orbiting the Sun at between 30 and 50 AU form the Sun. Hence the heliopause seems to be a fair choice for the boundary of the Solar system.

But the gravitational field of the Sun has a reach far beyond the heliopause. The orbit of Sedna around the Sun has an estimated perihelion of 76 AU and a perihelion of 943 AU, and hence is large part of Sedna’s orbit is well beyond the heliopause. In fact the Sun’s gravity is in no way affected by the existence of the heliopause. Actually if there were no other stars in the universe, the Sun’s gravity would reach to infinity, though it would still decrease according to an inverse square law.

Astronomers hypothesize that there is a cloud around the Sun, at around 50,000 to 100,000 AU distance, which referred to as the Oort cloud. The Oort cloud is believed to house trillions of objects large than 1 kilometer. All these objects are orbiting the Sun, but what would be the largest possible distance of an orbit around the Sun?

Since the nearest star is roughly the size of the Sun, and is located at about four light years away, the point at which both stars exert an equal gravity is located at about 2 light-years or 125,000 AU. If other star systems have also Oort clouds, those clouds might overlap each other. Consequently a group of Space Settlers which is moving outwards in small increments might enter another star system even without notice.

But even beyond those Oort clouds interstellar space is far from empty. Astronomers speculate that the number of rogue planets, i.e. planets who do not orbit any start but directly around the center of the galaxy, is twice to 100,000 times greater than the numbers of stars in our galaxy. Though the closest known rogue planet is located at about 100 light-years away, there is no particular reason to assume such planet could not be found closer to our Solar System. Only because rogue planets do not radiate much light, they are hard to detect.

For interstellar colonists such a rogue planet might be an attractive place to settle. Enough resources for hundred or even thousands of years, and while the rogue planet continues its way through the galaxy the might came close the another star system. At that point they could make a jump to that star system, if they would wish so.

Though interstellar space is far from empty, we should nevertheless realize that interstellar travel and colonization is an endeavor for the far future and it will probably not happen in this century, maybe not even during the next thousand years. Instead current plans for space colonization should focus on our own Solar System.

New method for producing stem cells

Unfortunately, this sounded too good to be true. Other scientists have failed to reproduce these results and ultimately the scientists involved had to retract their article. [update January 2, 2015]

Japanese scientists claim to have developed a new method to create human “embryonic-like” stem cells, without the ethical concerns of using real human embryos. Induced pluripotent stem cells have been considered as the solution for the controversial use of human embryos as source for stem cells for medical treatments, and for years scientists have been developing techniques to create such induced pluripotent stem cells. But until now these methods required the genetic engineering of adult cells, the Japanese have now found a method to change adult cells into stem cells without genetic engineering.

According to The Independent the scientists have succeeded to create induced pluripotent stem cells, just by bathing adult cells in a weak acid for half an hour. This new development is quite promising, if this method really works then stem cell therapy has the potential to become a widespread and reasonably cheap treatment for a wide variety of diseases.

The two main competitors of this technique, therapeutic cloning and traditional induced stem cells, are quite expensive. In “classic” induces pluripotent stem cells, complicated genetic engineering techniques are required, which demand skilled personal. And further genetic engineering is to a certain degree gambling, the genes have to get into the right place, or it will fail.

And besides the ethical controversy surrounding therapeutic cloning, this method has a serious drawback: the need for a huge amount of human egg cells. Harvesting human egg cells is not easy, since this requires surgery. And it’s questionable that there will be many women willing to sell or donate their eggs for this purpose.

A cheap and reliable supply of stem cells is beneficial for the field of tissue engineering, the creation of tissues and organs outside the human body.

Uterine transplants: a first step towards male pregnancy?

In Sweden nine women have received a uterine transplant, with the intend of getting pregnant very soon. According to the BBC the nine women were either born without a uterus, or had their own uterus been removed for medical reasons. Uterine transplants are a new area of medical science, earlier attempts in Saudi Arabia and Turkey have failed.

But suppose that the Swedish experiment works, after all organ transplants have a history of failure and ultimate success, then it will be possible to transplant uteri into males as well. Most academic discussions about male pregnancy, are about ectopic pregnancies (i.e. implantation of the embryo outside the uterus). But since ectopic pregnancies are usually lethal, no serious attempt has been made to induce such pregnancy in a male. Only a few ectopic pregnancies have resulted in live birth.

However, with uterine transplants the whole problem of ectopic pregnancies is avoided. If successful in women, there’s from a medical point of view no reason to refuse such treatment to males. Whether transplanting uteri into males is desirable, is a totally different matter.