The geometry and the orb
A square is ninety degrees, a quarter of the zodiac, and the orb allowed here is seven. Squares join signs of the same mode in incompatible elements. Cardinal to cardinal, fixed to fixed, mutable to mutable: Aries to Capricorn, Leo to Taurus, Virgo to Gemini. The two signs go about things the same way and want completely different outcomes, and that is the entire mechanical basis for the friction.
In each lunar cycle the Moon squares Mars twice, once approaching the opposition and once leaving it. The aspect appears in charts at an ordinary rate, so having it is not a distinguishing fact in itself.
A square that spans a sign boundary breaks the mode agreement and should be read lightly. A Moon at twenty eight degrees of Taurus with Mars at two degrees of Virgo is technically within orb and structurally nothing like a square, since those two signs are in a trine relationship by sign.
Why friction is the point
The Moon is the involuntary layer: what you need, what you are used to, the response that arrives before you have made a decision. Mars is the capacity to assert, to cut, to force an outcome. A square puts them ninety degrees apart, where neither is visible from the other's position, so each interrupts the other without warning.
The classic descriptions are impatience, a low threshold for provocation, and difficulty resting. The more careful version is that the person is never allowed to leave the pairing alone. Where a trine between these two supplies energy that need never be examined, a square supplies a problem that keeps presenting itself, and the tradition treats repeated presentation as the reason square aspects tend to produce developed skill in their subject.
None of that makes the aspect good or bad. It makes it active. The tradition's own position is that hard aspects describe pressure and say nothing on their own about what the pressure produces.
Dignity, house and the rest of the chart
Mars in Aries or Scorpio brings a square with weight behind it, and the friction reads as force meeting an obstacle. Mars in Cancer, its traditional fall, gives a square where the assertion is indirect and comes out sideways, which is a substantially different description of the same ninety degrees. Mars exalted in Capricorn produces the version most often described as hard work rather than temper.
Houses set the subject. A Moon in the sixth squaring a Mars in the ninth is a running argument between routine and travel or study. A Moon in the fourth squaring a Mars in the first turns it domestic and personal. Supporting aspects matter too: a square that also receives a trine from Saturn is usually read as pressure with a container around it.
Speed, retrograde Mars and your own orb
Mars covers about half a degree a day at normal speed and less near a station, while the Moon covers roughly thirteen. The Moon is therefore always the body closing or opening the angle, and the applying or separating distinction is easy to establish. Applying aspects are traditionally read as the stronger of the two.
Mars is retrograde for around two months in every twenty six. A retrograde Mars in a square is conventionally read as force that is withheld or redirected rather than discharged, which usually shows as delay rather than absence.
Treat a square inside three degrees as a genuine structural feature. Between four and five it competes with the rest of the chart. At six or seven, check whether the mode agreement still holds before reading it at all. The widget above gives the separation, both signs, both houses and the Mars condition at your birth.
Questions people ask about this
What does Moon square Mars mean?
It means the Moon and Mars were about ninety degrees apart at birth, within seven degrees of orb. The tradition reads it as instinctive need and assertive drive obstructing each other, usually out of each other's sight.
Is Moon square Mars a difficult aspect?
It is described as a pressured one. Astrologers class it as hard because it demands a response, but the tradition does not treat pressure as a verdict, and the result is held to depend on dignity, house and the rest of the chart.
How does it differ from the conjunction?
A conjunction fuses the two bodies so the person cannot separate the reaction from the drive. A square keeps them apart at an angle where each disrupts the other, which tends to be more noticeable and more contested internally.
Does Mars in Cancer change the reading?
Yes. Mars is in its fall in Cancer by the traditional scheme, and a square involving it is usually described as assertion that comes out indirectly rather than head on. The geometry is identical, the description is not.
What counts as a tight orb here?
Inside three degrees is tight enough to treat as a defining feature. Four or five is a working aspect. Six or seven is a background note, particularly if the square has crossed a sign boundary.
Does it matter whether the aspect was applying?
The tradition says so. An applying square, with the Moon still closing towards ninety degrees, is conventionally read as stronger than a separating one that has already passed exactness.