ACT Science : Earth and Space Sciences
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Example Questions
Example Question #21 : Earth And Space Sciences
A rover on Mars tests the soil on the planet in Gale Crater. An instrument on the rover dectects steep spikes in methane levels in the soil within 60 days. Additionally, satellite measurements from the area detect unusual plumes of methane from this specific area, which scientists suggest may have once contained an ancient freshwater lake. Two different scientists discuss whether this evidence is conclusive of the existence of life on the planet.
Scientist 1
This is the first evidence that organic life exists on Mars. On Earth, 95% of methane gas is produced by microbial organisms, which points towards the presence of similar biological processes on Mars. The rover has also found evidence of water bound to soil in the crater, and pictures showing carvings in the sides of the crater walls suggest the existence of once-flowing water. Because this water could have supported life in the crater, this methane originated from a bacterial source and shows there is life on the planet.
Scientist 2
There is no evidence of life on Mars. These methane spikes came from organic matter left behind from recent meteor impacts as they degraded in the sun's rays. Although the crater was once filled with water, now all water is bound to minerals in the soil and it not accessible. Methane has also been measured on planets such as Saturn, Uranus, and Neptune, which have conditions too hostile to support life. There is not even enough evidence to suggest that the original water in the crater could have supported life.
According to Scientist 1, which of the following must be present if there is life on Mars?
Methane
Organic matter from meteor impacts
Flowing water
Minerals in the soil
Methane
The scientist uses the presence of methane to support the exisetnce of life on Mars. He or she does not acknowledge flowing water to be currently on Mars. The other two choices are mentioned by Scientist 2.
Example Question #952 : Act Science
In describing how layers of earth are formed in a valley in southern Tanzania, two scientists provide separate explanations.
Scientist 1: Over time, sediments accumulate on the ground due to wind or water carrying those sediments to or from the valley. As external conditions change over time, new sediments come in and cover the old layer of sediment, creating a boundary between the older layer and the newer layer. This process continues, creating what we know as the layers of sediment on Earth. These layers remain in place indefinitely due to the weight of new layers being added on top of them.
Scientist 2: Sediments accumulate in the valley due to a variety of weather or climate conditions. As climate changes over time, different types of sediments may be introduced to the valley. Sediments can shift within the ground according to their density when water accumulates within the ground, causing layers to mix, blur, and sometimes switch.
On which of the following statements are the two scientists most likely to agree?
Weather conditions are not important to consider in the formation of sediment layers.
An object found in a lower layer of ground is necessarily older than an object found in a layer closer to the surface.
The process of sediment setting in the valley takes many years.
Sediment density is important in determining the sediment makeup of the valley.
The process of sediment setting in the valley is a process whose length depends on weather conditions.
The process of sediment setting in the valley takes many years.
The correct answer is "The process of sediment setting in the valley takes many years." Both scientists refer to climate changes being important in the sediment makeup of the valley. Climate changes take a very long time, and therefore it is likely that both scientists would agree with the above statement. The other responses are either points that are irrelevant to the passage, or with which only one or neither of the scientists would likely agree according to the information provided.
Example Question #23 : Earth And Space Sciences
In describing how layers of earth are formed in a valley in southern Tanzania, two scientists provide separate explanations.
Scientist 1: Over time, sediments accumulate on the ground due to wind or water carrying those sediments to or from the valley. As external conditions change over time, new sediments come in and cover the old layer of sediment, creating a boundary between the older layer and the newer layer. This process continues, creating what we know as the layers of sediment on Earth. These layers remain in place indefinitely due to the weight of new layers being added on top of them.
Scientist 2: Sediments accumulate in the valley due to a variety of weather or climate conditions. As climate changes over time, different types of sediments may be introduced to the valley. Sediments can shift within the ground according to their density when water accumulates within the ground, causing layers to mix, blur, and sometimes switch.
Which of the following statements would Scientist 1 most likely support while Scientist 2 would not?
The sediment layers formed in this valley have blurred boundaries that do not clearly mark shifts in weather/climate conditions.
The sediment layers formed in this valley have distinct boundaries that mark significant shifts in weather/climate conditions.
A decade of high rainfall followed by a decade of drought would affect the sediment layers in the valley.
Sediment layer formation is a long-term process.
Sediment properties are the most important factor in determining layer composition.
The sediment layers formed in this valley have distinct boundaries that mark significant shifts in weather/climate conditions.
The correct answer is "The sediment layers formed in this valley have distinct boundaries that mark significant shifts in weather/climate conditions." Assuming Scientist 1 is correct, layers that form do not change once new layers are formed on top of them. This would suggest that when changes do occur that affect the sediment composition, this change is defined by a boundary that does not change over time. Scientist 2 would likely disagree with this statement. This is because Scientist 2 makes the claim that sediment shifts around after it has settled into a layer, which would likely blur any boundaries established by previous shifts in sediment composition.
Example Question #24 : Earth And Space Sciences
In describing how layers of earth are formed in a valley in southern Tanzania, two scientists provide separate explanations.
Scientist 1: Over time, sediments accumulate on the ground due to wind or water carrying those sediments to or from the valley. As external conditions change over time, new sediments come in and cover the old layer of sediment, creating a boundary between the older layer and the newer layer. This process continues, creating what we know as the layers of sediment on Earth. These layers remain in place indefinitely due to the weight of new layers being added on top of them.
Scientist 2: Sediments accumulate in the valley due to a variety of weather or climate conditions. As climate changes over time, different types of sediments may be introduced to the valley. Sediments can shift within the ground according to their density when water accumulates within the ground, causing layers to mix, blur, and sometimes switch.
On which of the following points would the two scientists most likely disagree?
The types of sediments found in the valley are affected by climate.
The process of forming sediment layers in this valley takes a very long time.
Heavier sediments are usually found lower in a cross section of the ground of this valley.
Sediments in this valley are highly varied.
A cross-section of the ground layers in this valley reveals layers that are chronological in order of youngest nearest the surface to oldest at the greatest depths.
A cross-section of the ground layers in this valley reveals layers that are chronological in order of youngest nearest the surface to oldest at the greatest depths.
The answer is "A cross-section of the ground layers in this valley reveals layers that are chronological in order of youngest nearest the surface to oldest at the greatest depths." Scientist 1 states that the layers in the valley do not change after they are formed due to the weight of the above layers. This would indicate that a cross-section of the layers of earth in this valley would be chronological—older sediment would be found lower on the cross-section. Scientist 2, however, claims that although the layers may begin chronologically, factors such as the sediment's density can influence the makeup of the ground. This means that Scientist 2 would likely disagree that a cross section would be chronological because, assuming Scientist 2's statement is correct, the layers could switch around over time.
Example Question #22 : Earth And Space Sciences
In describing the physics involved in sending a satellite into orbit, two scientists express their opinions.
Scientist 1: Two important factors need to be considered when working with a satellite: its orbital radius 
Scientist 2: Orbital radius of a satellite is not something that can be controlled by anything but orbital speed and the mass of the object being orbited. A satellite orbiting earth can only change its orbital radius by changing its orbital speed.
A company has plans to send a satellite into orbit that will collect solar radiation for scientific study. The day before launch, the company wants to add some heavy equipment to the satellite without changing their predictions for the satellites orbital radius or speed. What would the two scientists say in response to this last-minute change?
Scientist 1: You do not need to adjust your predictions; Scientist 2: You must adjust your predictions for orbital radius and speed.
Both Scientist 1 and Scientist 2: You must adjust your predictions for orbital radius and speed.
Both Scientist 1 and Scientist 2: You do not need to adjust your predictions.
More information is needed such as the mass of the equipment added.
Scientist 1: You must adjust your predictions for orbital radius and speed; Scientist 2: You do not need to adjust your predictions.
Scientist 1: You must adjust your predictions for orbital radius and speed; Scientist 2: You do not need to adjust your predictions.
The correct answer is that Scientist 1 would likely advise the company to redo their calculations since they have now altered the mass of the satellite, and this will affect the predicted orbital radius and speed; however, Scientist 2 argues that satellite mass does not matter, so Scientist 2 will likely say that this change will not affect the project.
Example Question #961 : Act Science
In describing the physics involved in sending a satellite into orbit, two scientists express their opinions.
Scientist 1: Two important factors need to be considered when working with a satellite: its orbital radius
Scientist 2: Orbital radius of a satellite is not something that can be controlled by anything but orbital speed and the mass of the object being orbited. A satellite orbiting earth can only change its orbital radius by changing its orbital speed.
Scientists have recently discovered two comets that orbit Earth at such similar distances that any alterations in their distances would cause them to eventually collide. The two comets differ in size: one is nearly one hundred times as massive as the other. Nevertheless, both comets have been observed to travel at nearly the same speed. Whose hypothesis does this information support?
Scientist 1's hypothesis
Neither Scientist 1's nor Scientist 2's hypothesis
Both Scientist 1's and Scientist 2's hypotheses
More information is needed to support or refute either scientist's claims.
Scientist 2's hypothesis
Scientist 2's hypothesis
The correct answer is that this information supports Scientist 2's hypothesis. Scientist 2 argues that mass of a satellite does not affect its orbital radius or orbital speed. This we can extrapolate to also apply to comets. This is the important step. Once we have done that, it becomes clear that this new information supports Scientist 2's claim.
Example Question #961 : Act Science
Two scientists are interesting in studying the orbits of Jupiter's moons around Jupiter. Based on their own observations, the two scientists express their conclusions below:
Scientist 1: The moons of Jupiter vary greatly in size and mass and yet all have very different orbital radii (distances from Jupiter) which show no correlation with each moon's mass. This is likely attributed to the fact that while they have different masses, they are very small in comparison to the mass of Jupiter, so we can say that, relative to Jupiter's mass, the masses of Jupiter's moons are essentially equivalent. Jupiter's moons also vary greatly in the speed at which they orbit Jupiter. Unlike mass, this does correlate with orbital radius. A greater speed corresponds to a smaller orbital radius.
Scientist 2: Orbital radius is a quantity that does not depend on the orbiting object's mass. Instead, it depends on the mass of the central object (Jupiter, in this case) and the speed of the orbiting object. If, for example, Europa (one of Jupiter's moons) were orbiting a planet of half the mass of Jupiter at the same speed, it would have half the orbital radius. On the other hand, if Europa were orbiting Jupiter and Europa suddenly doubled its rotational speed, its orbital radius would decrease by a factor of four.
Upon which of the following statements are both Scientist 1 and Scientist 2 most likely to agree?
Orbital radius and the mass of the orbiting object are inversely related.
Orbital radius and orbital speed are directly related.
Orbital radius and orbital speed are inversely related.
There is no relationship between orbital radius and orbital speed.
Orbital radius and the mass of the orbiting object are directly related.
Orbital radius and orbital speed are inversely related.
The correct answer is that orbital radius and orbital speed are inversely related. Scientist 1 asserts that a greater speed results in a smaller orbital radius, implying an inverse relationship. Scientist 2 states the same thing in more explicit terms.
Example Question #962 : Act Science
Two scientists are interesting in studying the orbits of Jupiter's moons around Jupiter. Based on their own observations, the two scientists express their conclusions below:
Scientist 1: The moons of Jupiter vary greatly in size and mass and yet all have very different orbital radii (distances from Jupiter) which show no correlation with each moon's mass. This is likely attributed to the fact that while they have different masses, they are very small in comparison to the mass of Jupiter, so we can say that, relative to Jupiter's mass, the masses of Jupiter's moons are essentially equivalent. Jupiter's moons also vary greatly in the speed at which they orbit Jupiter. Unlike mass, this does correlate with orbital radius. A greater speed corresponds to a smaller orbital radius.
Scientist 2: Orbital radius is a quantity that does not depend on the orbiting object's mass. Instead, it depends on the mass of the central object (Jupiter, in this case) and the speed of the orbiting object. If, for example, Europa (one of Jupiter's moons) were orbiting a planet of half the mass of Jupiter at the same speed, it would have half the orbital radius. On the other hand, if Europa were orbiting Jupiter and Europa suddenly doubled its rotational speed, its orbital radius would decrease by a factor of four.
Over which of the following statements are the two scientists most likely to disagree?
Europa is an ideal example for examining the orbits of Jupiter's moons.
In general, orbital radius does not depend on the mass of the orbiting object.
In general, orbital radius does not depend on the mass of the central object.
In general, orbital radius depends on the mass of the orbiting object.
In general, orbital radius does not depend on an object's orbital speed.
In general, orbital radius depends on the mass of the orbiting object.
The correct answer is the statement "orbital radius depends on the mass of the orbiting object." Although Scientist 1 posits that in the case of a massive central object such as Jupiter, the masses of orbiting objects around that central object do not significantly affect orbital radius, Scientist 1 does so with the underlying assumption that normally the mass of the orbiting object does play a role in orbital radius; however, Scientist 2 expresses the opposite opinion, saying explicitly that orbital radius does not depend on the mass of the orbiting object. For the record, Scientist 2 is correct.
Example Question #963 : Act Science
Two scientists are interesting in studying the orbits of Jupiter's moons around Jupiter. Based on their own observations, the two scientists express their conclusions below:
Scientist 1: The moons of Jupiter vary greatly in size and mass and yet all have very different orbital radii (distances from Jupiter) which show no correlation with each moon's mass. This is likely attributed to the fact that while they have different masses, they are very small in comparison to the mass of Jupiter, so we can say that, relative to Jupiter's mass, the masses of Jupiter's moons are essentially equivalent. Jupiter's moons also vary greatly in the speed at which they orbit Jupiter. Unlike mass, this does correlate with orbital radius. A greater speed corresponds to a smaller orbital radius.
Scientist 2: Orbital radius is a quantity that does not depend on the orbiting object's mass. Instead, it depends on the mass of the central object (Jupiter, in this case) and the speed of the orbiting object. If, for example, Europa (one of Jupiter's moons) were orbiting a planet of half the mass of Jupiter at the same speed, it would have half the orbital radius. On the other hand, if Europa were orbiting Jupiter and Europa suddenly doubled its rotational speed, its orbital radius would decrease by a factor of four.
If Jupiter's mass were to suddenly decrease significantly, with which statement would Scientist 1 most likely agree and Scientist 2 most likely disagree?
The orbital radii of Jupiter's moons would begin to correlate with their masses.
The orbital radii of Jupiter's moons would increase.
The orbital radii of Jupiter's moons would decrease.
The orbital speeds of Jupiter's moons would increase.
The orbital speeds of Jupiter's moons would decrease.
The orbital radii of Jupiter's moons would begin to correlate with their masses.
The correct answer is the statement that the orbital radii of Jupiter's moons would begin to correlate with their masses. Scientist 1 makes the claim that the only reason this correlation is not observed in Jupiter's case is that Jupiter's mass is very large relative to its moons. Therefore, if Scientist 1 were correct, we would expect this correlation to become visible once Jupiter's mass were small enough that the differences in its moons' masses would be significant. Scientist 2 disagrees and says that there is no relationship between mass of an orbiting object and its orbital radius. Therefore, Scientist 2 would not agree with this statement.
Example Question #964 : Act Science
Two scientists are interesting in studying the orbits of Jupiter's moons around Jupiter. Based on their own observations, the two scientists express their conclusions below:
Scientist 1: The moons of Jupiter vary greatly in size and mass and yet all have very different orbital radii (distances from Jupiter) which show no correlation with each moon's mass. This is likely attributed to the fact that while they have different masses, they are very small in comparison to the mass of Jupiter, so we can say that, relative to Jupiter's mass, the masses of Jupiter's moons are essentially equivalent. Jupiter's moons also vary greatly in the speed at which they orbit Jupiter. Unlike mass, this does correlate with orbital radius. A greater speed corresponds to a smaller orbital radius.
Scientist 2: Orbital radius is a quantity that does not depend on the orbiting object's mass. Instead, it depends on the mass of the central object (Jupiter, in this case) and the speed of the orbiting object. If, for example, Europa (one of Jupiter's moons) were orbiting a planet of half the mass of Jupiter at the same speed, it would have half the orbital radius. On the other hand, if Europa were orbiting Jupiter and Europa suddenly doubled its rotational speed, its orbital radius would decrease by a factor of four.
According to Scientist 2, how can we best describe the relationship between an orbiting object's orbital speed and that object's orbital radius?
They are inversely and exponentially related.
There is no relationship.
They are directly and exponentially related.
They are inversely and linearly related.
They are directly and linearly related.
They are inversely and exponentially related.
The correct answer is that the two variables are inversely and exponentially related. Like Scientist 1, Scientist 2 makes it clear that as orbital speed increases, orbital radius decreases. However, Scientist 2 also specifies by how much. When orbital speed doubles, orbital radius decreases by a factor of four. The most likely relationship of the answers given therefore is an inverse relationship that is also exponential.
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