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Could Aliens be Living in Our Solar System?

September 23, 2016

Image Credit: NASA/JPL-Caltech

http://www.jpl.nasa.gov/visions-of-the-future/

Water: the ultimate resource. We depend on it to survive, but Earth is not the only place with a substantial amount of water. Buckle up, because I want to tell you about my favorite moon, Europa.

Europa is one of the moons of Jupiter. It is approximately 4.5 billion years old (about the same age as Jupiter) and is about 485 million miles from the sun. It is the smallest of the Galilean moons with a diameter of 1900 miles (smaller than Earth’s moon but larger than Pluto). Europa looks like a dead, frozen, wasteland covered in large cracks and fractures in the ice, but it is exactly for this reason why it is so cool (literally and figuratively). These cracks are likely caused by tides in an ocean that lies buried underneath Europa’s icy surface. Europa’s tide is the result of host planet Jupiter. Jupiter’s gravity lifts and lowers the sea level causing cracking in the ice. Below the ice and ocean is a rocky interior and inside that is an iron core [1].

pia20707_fig1_thumb

Image Credit: NASA/JPL-Caltech/SwRI/MSSS

http://photojournal.jpl.nasa.gov/catalog/PIA20707

picture3

Image Credit: NASA

http://spaceplace.nasa.gov/europa/en/

Ok, so you might be thinking, “that’s kinda cool, a frozen moon. Why do I care?” Well, you should care because Europa’s subsurface ocean hosts the possibility of life. That makes Europa a possibly habitable location for us humans (in the future though, cause we are no where near that yet), which is awesome.

The ocean beneath the surface is widely believed to be salty liquid water which is a big deal (but not yet known for certain since we haven’t sent any missions directly to Europa  thus-far). In a recent study done by NASA’s Jet Propulsion Laboratory (Vance et al., Geophysical controls of chemical disequilibria in Europa), the researchers calculated the potential amount of hydrogen that could be produced from interactions of seawater with the rock below it.This process of interaction is called serpentinization. NASA also looked into oxidants in Europa’s ocean. Jupiter, being the massive gas giant that it is, bathes Europa in radiation from it magnetosphere (Earth actually has this type of radiation too called the Van Allen belts, although they are about a thousand times weaker than Jupiter’s).  This radiation can split apart water ice molecules and create oxidants. One of the lead authors of NASA’s study, Steve Vance, said, “If the rock is cold, it’s easier to fracture. This allows for a huge amount of hydrogen to be produced by serpentinization that would balance the oxidants in a ratio comparable to that in Earth’s oceans”. The balance between hydrogen and oxidants is an indicator to the energy available for life [2]. However since no spacecrafts have been sent to Europa to investigate this, it is currently unknown if serpentinization occurs (several spacecrafts have done flybys such as Pioneer 10 and 11, Voyager 1 and 2, and Galileo [1] ).

NASA is planning an orbital reconnaissance mission of Europa called the Europa Clipper with the main goal of investigating the habitability of Europa. The Clipper will have 45 low-altitude flybys over the course of 3.5 years. The clipper will have three main objectives [3] : (1) to investigate the ice shell and ocean, (2) investigate the composition, and (3) investigate the geology of Europa. Essentially, NASA wants to confirm what they think they know about the structure and composition of Europa and how it’s layers interact (like the rocky interior, the ocean, and the icy shell) both mechanically and chemically, and determine the effect Jupiter’s radiation has on Europa. This will give insight to the habitability of Europa. There will be nine scientific instruments aboard to try meet these scientific objectives.

picture5

Image Credit: NASA/JPL-Caltech

http://www.jpl.nasa.gov/news/news.php?feature=4627

The Europa Clipper’s launch date is not yet determined, but it is likely to be in the early 2020s and would arrive 6-9 years later depending on the launch vehicle [4]. There is still A LOT of work needed to be done on the mission planning, but I’m very optimistic that it will yield in fascinating results, maybe even giving us significant insight to if we are alone in the solar system.

Here is a NASA/JPL-Caltech video about the Clipper:

References:

  1. Howell, E. Europa: Facts about Jupiter’s icy moon and its ocean. Retrieved September 4, 2016, from http://www.space.com/15498-europa-sdcmp.html
  2. Greicius, T. (2016, May 16). Europa’s ocean may have an Earthlike chemical balance. Retrieved September 4, 2016, from https://www.nasa.gov/feature/jpl/europas-ocean-may-have-an-earthlike-chemical-balance
  3. The Europa Clipper. (2013, June ). Retrieved September 4, 2016, from http://www.lpi.usra.edu/opag/jul2013/presentations/Clipper_Summary.pdf
  4. Europa Clipper Update. (2015, February 19). Retrieved September 4, 2016, from http://www.lpi.usra.edu/opag/feb2015/presentations/04_Clipper%20OPAG%20Feb%202015.pdf

 

 

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Sage Kemmerlin
About Author

Sage Kemmerlin – Sage is an Earth and Atmospheric Science major, specializing in geophysics, at Georgia Tech. In her spare time, she likes to paint and draw, go backpacking, watch various things on Netflix, make dumb jokes, and (when she has the money) travel.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.